Shaft tombs are by far the most numerous of the 20,000 graves found at Bab edh-Dhra. They are also the oldest: The earliest date from around 3200 B.C. The shaft portion of a shaft tomb is about three feet in diameter, six feet deep, and is dug straight down into the ground. Each shaft has from one to five burial chambers which branch out from its base. Blocking stones were used to close off each burial chamber entrance. Here one is about to be removed.