The engineers dug into the basaltic rock, planted explosives and blew them up to create craters.
Over the course of four months, they blasted 143 craters between five and forty feet in diameter.
The distribution and size of the craters were not arbitrarily chosen.
They were produced at 1:1 scale to duplicate a small area of the proposed landing site.
This area became known as the Cinder Lake Crater Field.
The second site measured 1,200 feet square and contained 354 craters.
Slopes of the craters were used to test the lunar modules and the rovers.
The last training took place in 1972 for Apollo 17, the final of the Apollo mission.
Now fifty years later, much of the craters have eroded away, with only the largest craters distinguishable.
First crater field
Second crater field
