Solomon's Quarries are also referred to as "Zedekiah's Caves", having said to have been an escape route for the King whilst fleeing from the Babylonians.
The quarries are in fact one giant underground cavern running below much of the Muslim quarter of Jerusalem's old city. It is part of the quarry that extends up to the Garden Tomb's Golgotha on the other side of the street from its entrance, and could actually have been used in the first temple period because of the hardness of the limestone found there - a valuable building material.
The cave is popular with freemasons