Pool of Siloam

The term Pool of Siloam refers to a number of rock-cut pools on the southern slope of the Wadi Hilweh, considered by some archaeologists to be the original site of Jerusalem, located outside the walls of the Old City to the southeast. The pools were fed by the waters of the Gihon Spring, carried there by the Siloam Tunnel.

The Lower Pool or "Old Pool" was historically known as Birket el Hamra, literally "the red pool".

Source: Wikipedia