Project Y Los Alamos National Laboratory
Learn more about the Manhattan Project National Historic Park
Discover the stories and places behind the Manhattan Project and how they shaped the world we live in today.
Manhattan Project National Historical Park Virtual Tour
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Manhattan Project National Historical Park
SITE 1
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V Site
SITE 3
Q-Site
SITE 2
Gun Site
Manhattan Project researchers developed GunSite, known in 1943 as Anchor Ranch Proving Ground, to design and test nuclear weapon prototypes.
SITE 4
K-Site
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S-Site
SITE 5
SITE 6
Concrete Bowl
Project Y: Los Alamos National Laboratory
VIDEO OVERVIEW
Quonset Hut
SITE 7
Department of Energy
The Manhattan Project National Historical Park tells the story of the people, the events, and the science and engineering that led to the creation of the atomic bombs that helped bring an end to World War II. Structures and landscapes from that era allow visitors to explore how the creation of these weapons changed the world and the United States’ role in the world community, and address the subsequent controversy and contribution of the Project to the annals of history and the world in which we live. In Los Alamos, the park experience is a partnership among the Department of Energy, the National Park Service, private landowners, and Los Alamos County. In Los Alamos, the Department of Energy is developing phased access to its properties that are currently inaccessible. In the interim, visitors can see the properties on this walking tour in the city center, visit the Bradbury Science Museum, and the Los Alamos History Museum
1 - Downtown Los Alamos
7 - Pond Cabin
2 - Battleship Bunker
8 - Q-Site
3 - Concrete Bowl
9 - The Quonset Hut
4 - Gun Site
10 - S-Site
5 - K-Site
11 - Slotin Building
6 - L-Site
12 - V-Site
The Manhattan Project National Historical Park tells the story of the people, the events, and the science and engineering that led to the creation of the atomic bombs that helped bring an end to World War II. Structures and landscapes from that era allow visitors to explore how the creation of these weapons changed the world and the United States’ role in the world community, and address the subsequent controversy and contribution of the Project to the annals of history and the world in which we live.
Preserving and sharing the nationally significant historic sites, stories, and legacies associated with the top-secret race to develop an atomic weapon during World War II.
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TA-18-2 was constructed in 1944 to support implosion diagnostic tests related to Fat Man design development. Experiments using the magnetic method, carried out at Pajarito Site, detected changes in a magnetic field during a high-explosives shot. TA-18-2 is a robust, cast-in-place concrete bunker. It is known as a battleship building because the west end of the building is bow shaped and shielded with steel plate.
Battleship Bunker
In Los Alamos, the park experience is a partnership among the Department of Energy, the National Park Service, private landowners, and Los Alamos County. In Los Alamos, the Department of Energy is developing phased access to its properties that are currently inaccessible. In the interim, visitors can see the properties on this walking tour in the city center, visit the Bradbury Science Museum, and the Los Alamos History Museum
Downtown Los Alamos Sites
Plan your visit
Two Mile Mesa Site, also known as TA-6, was used as an outdoor research area to develop plutonium recovery methods in the event that the Trinity test failed. One of the most visible legacies of this research is a large, 200-ft-diameter concrete bowl built in 1944. The bowl was used for the water recovery method, which involved detonating high explosives experiments using natural uranium as a stand- in for plutonium. The test assemblies were placed in the center of the bowl in a redwood water tank...
During Project Y, Los Alamos researchers also developed the Gun Site, known in 1943 as Anchor Ranch Proving Ground, to design and test nuclear weapon prototypes. At this site, scientists, engineers, and ordinance experts conducted experiments on the inner workings of a “gun-type” atomic bomb design, hence the site’s name.
More than 12 testing areas were developed at Los Alamos in late 1944 and early 1945 to support the design of a new plutonium weapon. This research included the use of varied diagnostic methods to understand the inner workings of implosion, an inward explosive force that was key to the Fat Man weapon design. Built in late 1944, TA-11 supported experiments that relied on the betatron diagnostic method.
TA-12-4, built in 1944, is a firing pit constructed of heavy timber for use in high-explosives experiments that supported implosion research. The Los Alamos Terminal Observation Group used TA-12 as its firing site. Physical remains of explosives firing tests were examined after each shot, hence the term “terminal observation.” World War II facilities included the firing pit, a personnel shelter, and several storage buildings and magazines. The pit structure is 12-ft deep and capped with an 8-ft-square steel lid...
L-Site
Originally built in 1914 by Ashley Pond as an office for a private Sportman’s Club, the cabin was used by physicist Emilio Segrè’s group during the Manhattan Project to support plutonium chemistry research.
Pond Cabin
TA-14-6 is a small, wood-frame building that was constructed in 1944 as a darkroom and shop to support small scale implosion tests. At Q-Site (TA-14), cylinder implosions were studied using the flash photography method. This implosion diagnostic tool relied on high-speed photographic equipment, including the rotating prism camera. In addition to the flash photography implosion experiments, terminal observation experiments were also conducted at Q-Site. Wartime facilities included a control building...
Building TA-22-1, a Quonset™ hut, is one of the most historically significant properties at the Laboratory. Manhattan Project scientists and engineers worked on the final design of the Fat Man weapon in this facility, perfecting the “trap door” design shortly before the end of the war. Fat Man’s high-explosives sphere and associated components were assembled in this building and then transported to Tinian Island. After the war, the building was used as a detonator research facility for almost 40 years.
The Quonset Hut
TA-16-58, constructed in 1944, is a one-story, single-room, high-explosives storage magazine. This small building was constructed with a reinforced-concrete floor and walls. The magazine is encircled by a protective earthen berm, and its roof is built of wood to serve as an upwards path for the force of an accidental explosion. This building is the last remaining high-explosives facility built specifically to support S-Site operations during the Manhattan Project.
The high-bay addition at TA-18-1 was constructed in1946, at the end of the Manhattan Project era, and supported criticality research at the wartime Laboratory’s Pajarito Site. This building addition was the location of the May 21, 1946, criticality accident, which occurred during an experiment known as “dragon-type experiment” and led to the death of scientist Louis Slotin.
Slotin Building
V-Site was constructed to support the assembly of the Fat Man implosion weapon. It was also used to assemble the high-explosives sphere for the Trinity device or Gadget. The site originally consisted of six buildings, but four were destroyed during the May 2000 Cerro Grande Fire. The first building at V-Site was built in early 1944. TA-16-517, as it is known today, is a small triangular-shaped building surrounded by an earthen berm.
V-Site
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EXTERIOR
INTERIOR
Manhattan Project Staff constructed V-Site to support the assembly of the Fat Man implosion weapon. Staff members also used this site to assemble the high-explosives sphere for the Trinity device, or Gadget. Built in early 1944, the first building constructed on site is a small triangular-shaped structure surrounded by an earthen berm. Thisbuilding supported early test of the first Fat Man prototypes to ensure that key components could withstand cold temperatures and vibration of an airplane bomb-bay. Staff members also constructed shop buildings, a high-bay assembly building, and a covered storage area at V-Site inlate 1944 to support the assembly of the Trinity device. During the week of July 9, 1945, thehigh-explosives package for the Gadget was assembled at V-Site in the high-bay building (TA-16-516).
Security was crucial at V-Site—Manhattan ProjectStaff constructed a “no-peek” fence around the site to block views of combat units assembledand tested here. Today, a replicated fence and gate provide the same feel at V-Site. In 2007, LosAlamos National Laboratory replicated a section of “no-peek” fence and the entrance gate fromoriginal drawings on file with the Lab’s engineering records group.
These photos will be used by the Manhattan Project National Historical Park and Los AlamosNational Laboratory for public engagement including articles, web use, mobile applications, and othertypes of media. They will also be used to document this historic structure associated with the park.
Interior of V-Site’s high-bay building. Candy cookers similar to those Manhattan Project staff members used to melt high-explosives in the foreground.
Manhattan Project researchers developed GunSite, known in 1943 as Anchor Ranch Proving Ground, to design and test nuclear weapon prototypes. One of the earliest test facilities at Los Alamos, Gun Site earned its name because of its role in the development of the gun-type weapon, Little Boy, used against Japan in Hiroshima—the first nuclear weapon ever used in war. The buildings at this wartime technical area include standard proving-ground bunkers that are partially underground. Manhattan Project engineers constructed the buildings in a natural drainage—placing the buildings partially underground and positioning the tests above the roof level. This unique layout lessened the hazards associated with their experimentations using high-alloy gun tubes. Photo taken facing the exposed front entrance of Gun Site facing southwest and showing TA-8-1, TA-8-2, and TA-8-3.
Photo taken from insideTA-8-1, main facility at Gun Site. Up-close image of painted tool wall to show staff memberswhere to return used tools.
The test assemblies were placed in the center of the bowl in a redwood water tank on top of a wooden tower structure. Each shot used up to 10 pounds of explosives and up to 500 gallons of water. Shake tests of explosives and other test shots supporting wartime weapons research were also conducted at the structure. photo taken 1979
The bunkers at TA-18-2 are associated with the development of the “Fat Man” bomb, with criticality research, nuclear propulsion research, and the development of related health and safety protocols, and with nuclear safeguards and security. The six buildings represent important aspects of Los Alamos’s contribution to the history of World War II and the Cold War.
At Battleship Bunker, scientists devised new diagnostic tests to better understand implosion type technology. The magnetic method measured shock waves through disruptions in the magnetic field. Initially this method focused only on small scale implosion, but eventually the magnetic method provided valuable information about full-scale explosion assemblies.
The Battleship Bunker at TA-18-2 supported these tests and supplied project personnel with important information on implosion.
Concrete Bowl ›
‹ V-Site
A story that is often overshadowed when sharing Manhattan Project history is that of plutonium recovery. The Concrete Bowl helps bring that story to life. Throughout the Manhattan Project, uranium and plutonium were so rare and costly that scientists carefully conserved every gram. By the end of 1945, it cost an estimated $390 million to create the plutonium for the Manhattan Project—that is over $5 billion in today’s money! During the Trinity Test, scientists planned to carry out a test with half the world’s plutonium, so tensions were understandably high. If the Trinity Test did not succeed, project staff needed to recover the precious plutonium rather than lose it on a failed test. Manhattan Project researchers discussed several possible plutonium recovery approaches and tested any potential solutions that were not too far-fetched. One idea was the “water recovery method.”
For this method, staff members constructed a concrete bowl 200 feet in diameter and built a wooden water tank on a tower in the center. In this water tank, they placed a small-scale, industrial prototype of a bomb that contained natural uranium as a stand-in for plutonium. Researchers then detonated this mock-up with conventional explosives inside the water tank. The water from the explosion landed in this concrete reservoir and drained into the bowl’s filter system, where workers recovered the metal fragments. Scientists continued these water-recovery tests until early 1945, but after realizing this method was not feasible for a full scale nuclear test, they moved on to other potential recovery methods—including the infamous giant steel containment vessel known as “Jumbo.”
The Concrete Bowl remains in place today—an example of the wartime Laboratory’s practice of simultaneously testing different solutions to solve complex problems. In the 75 years since the bowl’s construction, weeds and trees took over and the local fauna discovered it as a reliable watering hole on the arid Pajarito Plateau.
Gun Site ›
‹ Battleship Bunker
Photo taken from inside TA-8-1,main facility at Gun Site. Beam on ceiling was used to move weapon components through the interior space and to a loading door.
Photo taken from inside TA-8-1, main facility at Gun Site. Up-close image of painted tool wall to show staff members where to return used tools.
K-Site ›
‹ Concrete Bowl
K-Site (TA-11-1) was built in 1944 and served as a control laboratory for the Betatron and Cloud Chamber firing experiments for implosion diagnostic tests. Constructed with heavily reinforced concrete walls, a compacted earthen berm covers the building’s roof and its north, east, and south sides. Photo taken facing east.
Candy cookers similar to those Manhattan Project staff members used to melt high-explosives
These photos will be used by the Manhattan Project National Historical Park and Los Alamos National Laboratory for public engagement including articles, web use, mobile applications, and othertypes of media. They will also be used to document this historic structure associated with the park.
An original lightning rod still stands at V-Site. Manhattan Project staff incorporated lighting protection systems near vulnerable sites. Lightning arrester systems had grounding wires leading to the ground.
K-Site (TA-11-3) housed the Cloud Chamber for the betatron diagnostic method. Located back to back with the betatron structure (TA-11-2),scientists would detonate the small-scale test implosion between the two buildings during the experiment. The betatron machine emitted X-rays at the instant of the explosion and the cloud chamber recorded the data. Today, the space between the two is filled. Image taken facing north.
K-Site (TA-11-2) housed the betatron machine. A newer exterior door and structure was added after the Manhattan Project. Front of structure—image taken facing south.
interior of the cloud chamber
Betatron interior
Betatron entrance
Betatron door
L-Site ›
‹ Gun Site
TA-12-4, built in 1944, is a firing pit constructed of heavy timber for use in high-explosives experiments that supported implosion research. The Los Alamos Terminal Observation Group used TA-12 as its firing site. Physical remains of explosives firing tests were examined after each shot, hence the term “terminal observation.” World War II facilities included the firing pit, a personnel shelter, and several storage buildings and magazines.
The pit structure is 12 feet deep and capped with an 8-ft-square steel lid. The sides of the pit are lined with 3/4-in. steel plate, which was designed to protect the structure from explosive blasts.
Pond Cabin ›
‹ K-Site
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The Pond Cabin was primarily used by Emilio Segré and his team as an office, library, and a place to relax as they studied the chemistry needed for the implosion type weapons that would become known as the Fat Man.
“It was a most poetic place,” Segrè recalled. “We went there by jeep every day. There was a bed in it. Somebody occasionally slept there”
Q-Site ›
‹ L-Site
Manhattan Project staff members constructed Q-Site (TA-14-6) in 1944 as a darkroom and shop to support small-scale implosion tests. It is a small, wood frame building. At Q-Site (TA-14), researchers studied cylinder implosions using the flash photography method. This implosion diagnostic tool relied on high-speed photographic equipment, including the rotating prism camera. In addition to the flash photography implosion experiments, scientists also conducted terminal observation experiments at Q-Site. Wartime facilities included a control building, high-explosives magazines, firing chambers, and this structure—the shop and darkroom building. Photo taken facing north.
Quonset Hut ›
‹ Pond Cabin
The Quonset Hut (TA-22-1) is one of the most historically significant properties at Los Alamos National Laboratory. At this site, Manhattan Project scientists, engineers, and military personnel worked on the final, trap door design of the Fat Man weapon. Leaving nothing to chance, Project Alberta staff trained the weapons assembly crew at Los Alamos under field conditions and in building types already in place in the Pacific. The Quonset hut in Los Alamos was similar to those the military constructed on Tinian Island—the base of operations for the combat use of the atomic weapons on Japan. Here, staff members assembled Fat Man’s high-explosives sphere and associated components and then transported them to Tinian Island. The structure rests on a concrete foundation and the frame isarch-shaped and covered with silver corrugated siding. Photo taken of front of building facing east.
Interior of Quonset Hut. An I-beam runs the length of the building. Manhattan Project staff hung the pre-assembled Fat Man weapon from this beam for assembly.
The Quonset Hut (TA-22-1) is one of the most historically significant properties at Los Alamos National Laboratory. At this site, Manhattan Project scientists, engineers, and military personnel worked on the final, trap door design of theFat Man weapon. Leaving nothing to chance, Project Alberta staff trained the weapons assembly crew at Los Alamos under field conditions and in building types already in place in the Pacific. The Quonset hut in Los Alamos was similar to those the military constructed on Tinian Island—the base of operations for the combat use of the atomic weapons on Japan. Here, staff members assembled Fat Man’s high-explosives sphere and associated components and then transported them to Tinian Island. The structure rests on a concrete foundation and the frame isarch-shaped and covered with silver corrugated siding. Photo taken of front of building facing east.
An I-beam runs the length of the building. Manhattan Project staff hung the pre-assembled Fat Man weapon from this beam for assembly.
S-Site ›
‹ Q-Site
Manhattan Project researchers constructed S-Site (TA-16-58) in 1944. This small building is a one-story, single-room, high explosives storage magazine with reinforced-concrete floor and walls. Photo taken facing the front doors of the magazine facing west.
Interior view of the one-room storage magazine. Manhattan Project Staff members built the magazine with reinforced concrete walls and a wooden roof to serve as an upwards path for the force of an accidental explosion. The wooden roof and concrete walls are visible.
The magazine is encircled by a protective earthen berm. Staff members built its roof out of wood to serve as an upwards path for the force of an accidental explosion. This building is the last remaining high-explosives facility built specifically to support S-site operations during the Manhattan Project.
The original siding that was painted green visible during the Manhattan Project. This was the original siding covered over on most structures.
Slotin Building ›
‹ Quonset Hut
On May 21st 1946, Louis Slotin was conducting an experiment called “tickling the dragon’s tail” involving a subcritical mass of plutonium and beryllium. When a screwdriver Slotin was holding slipped, a reaction occurred releasing a sudden burst of radiation. Louis Slotin died nine days later.
The Criticality Accident Mock-up was commissioned and created in 2018 as a teaching tool for workers at the Lab. The artifact is a striking visual and spatial aid to remind workers that tiny actions can have massive consequences and that not knowing what you don’t know can be the greatest threat. Slotin didn't know that standing just two feet further away from the experiment might save his life, but workers standing next to this model get a very personal, physical sense of how distance matters in their day-to-day operations.
A re-creation of the criticality experiment that claimed the life of Louis Slotin in May 1946
V-Site ›
‹ S-Site
Manhattan Project Staff constructed V-Site to support the assembly of the Fat Man implosion weapon. Staff members also used this site to assemble the high-explosives sphere for the Trinity device, or Gadget. Built in early 1944, the first building constructed on site is a small triangular-shaped structure surrounded by an earthen berm. This building supported early test of the first Fat Man prototypes to ensure that key components could withstand cold temperatures and vibration of an airplane bomb-bay. Staff members also constructed shop buildings, a high-bay assembly building, and a covered storage area at V-Site inlate 1944 to support the assembly of the Trinity device. During the week of July 9, 1945, the high-explosives package for the Gadget was assembled at V-Site in the high-bay building (TA-16-516).
Security was crucial at V-Site—Manhattan Project Staff constructed a “no-peek” fence around the site to block views of combat units assembled and tested here. Today, a replicated fence and gate provide the same feel at V-Site. In 2007, Los Alamos National Laboratory replicated a section of “no-peek” fence and the entrance gate from original drawings on file with the Lab’s engineering records group.
Battleship Bunker ›
‹ Slotin Building
