Hank Weber took this photo of the lava monument marking Ground Zero of the first atomic device ever exploded. The "gadget" as it was called was hoisted to the top of a 100 foot steel tower, directly above this marker. On July 16, 1945, at 0529:45 Hours, Mountain War Time, it was detonated with a yield of 19 kilotons equivalent TNT. The steel tower was mostly vaporized and the sand near the fireball melted into radioactive glass slag later named Trinitite. A nearby shelter preserves some of the desert floor as it looked when covered with Trinitite.
Outside the fence is the remains of Jumbo. Originally, the bomb was to be placed inside of Jumbo. Jumbo was a 214 ton steel cylinder designed to contain the plutonium if it failed to reach enough critical mass to sustain a runaway chain reaction. Plutonium doesn't occur naturally....it is man made. The small pit used in this device had cost billions of dollars to make, and the only other existing store of it was scheduled to go to Nagasaki in a couple of weeks, if Trinity worked. Jumbo was designed to keep the plutonium from being scattered over the desert and lost if the bomb was a dud.
But, confidence that the bomb would work continued to rise, and the idea of using Jumbo was abandoned. If Jumbo had been used, and the bomb worked, it would have added an additional 214 tons of radioactive debris floating over the New Mexico desert. An attempt to destroy Jumbo by exploding five 500 pound bombs inside failed....it only blew off the end caps.