The Hasmonean aqueduct cut into the bedrock in 150 BC is located north of the northwest corner of the Temple Mount. It brought water into the city from the pools located in the area. In 19 BC, Herod expanded the Temple Mount northward to include this area. At that time, the aqueduct was cut into, and the water was redirected. The walls and floor of this aqueduct have been worn smooth by water.
These pools of water, which are accessed through the Western Wall Tunnels, are located at the northwest corner of Herod’s Temple Mount. They were open reservoirs in the days of the Hasmoneans and connected to the aqueduct. The water was used as a moat on the north side of Fort Antonia in Herod’s day. In 135 AD, Hadrian built arched supports and vaults over these pools and used them as cisterns with a marketplace built over the tops of the arched vaults on the street level above.
The arch and vaulted ceiling built by Hadrian over the Hasmonean water reservoirs.