Archeologists from the Israel Antiquities Authority plan to excavate the site next week to learn more about the cistern, or underground water reservoir, that was unearthed Wednesday.

The cistern, which is 40 feet deep in some places, is close to the Basilica of the Annunciation, where Christians believe the Angel Gabriel appeared before the Virgin Mary and foretold the birth of Jesus.

On Tuesday, bulldozers tore out the foundations of a mosque that was being built without authorization next to the basilica. After demolition of the mosque foundation, a construction crew started work on a plaza for pilgrims at the site.

The workers found the Byzantine-era well, said archaeologist Dror Barshad.

Researchers rappelled into the dark cavern to have a closer look.

"It's built out of rock from the crusader period with an arched interior," said Uzi Shamir, a Israeli Housing Authority official involved in the plaza construction.