Citadel, Amman, Jordan
This large cistern, located to the right of the vestibule, was the primary water supply to the governor's palace. At 5m deep and 16m in diameter, it would have held just over 1,000 cubic meters, or approximately 250,000 gallons, of water. The cistern was fed by rainwater through an inlet channel, and could be entered for maintenance by the stairs shown in the photo. A column, whose stump is standing at the bottom of the cistern, measured the water level.