Cave of Aglauros
From Project Athinai
The cave where the nymph Aglauros was worshiped, was located on the north slope of the Akropolis Rock. It measured between 1 to 2.5 m wide, 18 m high and 35 m long. A stairway cut in the bedrock led from the top of the Akropolis, west of the House of the Arrephoroi, to the upper part of the cave. Other stairs were placed on wooden beams within the cave to give access to a spring. This spring was in use for about 40 years towards the end of the 13th century BC, during the Mycenaean period.
The cave was also accessible from the north face of the Akropolis rock through a circular entrance.
Travlos, John, Pictorial dictionary of Ancient Athens, Books that matter, New York, 1971, p. 72