This is the north end of Yucca Flat where most tests have been conducted. When atmospheric tests were banned in 1963, nuclear testing moved underground. The subterranean explosions left saucer-shaped craters varying in diameter and depth, depending upon the yield, depth of burial, and geology. The landscape created by these explosions was considered so moon-like that it was used for training the Apollo astronauts for their moon walks.
Photograph courtesy of National Nuclear Security Administration