Archaeologists have discovered a large public cistern from the time of the First Temple in Jerusalem’s Old City, the Israel Antiquities Authority said Thursday, offering new insight into the city’s water supply more than 2,500 years ago.

The cistern, which held 250 cubic meters of water, was discovered adjacent to the western side of the Temple Mount during an ongoing excavation at the site, the IAA said in a statement.

The discovery shows that the city’s water supply at the time did not rely solely on the Gihon Spring, Jerusalem’s only natural water source, but rather included large man-made reservoirs of the kind now uncovered, according to the IAA.

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The unique size of the cistern — the largest of its time to be discovered in the city — and its location suggest the possibility that it played a part in the ritual activities at the Temple, according to archaeologist Tsvika Tsuk of the Israel Nature and Parks Authority.

“It is possible that the large cistern found next to the Temple Mount was used in the daily operation of the Temple itself, and also served the pilgrims who came to the Temple and needed water for washing and drinking,” Tsuk said, according to the IAA statement.

The cistern was waterproofed with a yellowish plaster typical of the period, with handprints still visible on the walls, Tsuk said.

The First Temple was built around 950 BCE, according to the biblical record, and destroyed by a Babylonian army in 586 CE.

Construction of the Second Temple commenced some 50 years later. The Temple Mount as it currently exists dates to an expansion and renovation of the compound by Herod the Great five centuries after that, about 2,000 years ago.

The Second Temple was destroyed by Rome in 70 CE.

The excavation in which the cistern was found is being carried out by the Israel Antiquities Authority, an arm of the Israeli government, and is funded by the Elad Foundation.