The place
Underground structure with a tholos roof (a false dome formed by concentric rings of corbelled blocks) found about twenty metres from the south-western wall of the Acropolis of Circeii, within the circuit of the Cyclopean Walls. Already described in 1792 by the French archaeologist Petit-Radel, who gave it this curious name, the structure lacks the technical features typical of waterproofed cisterns; this has led some scholars to suggest a different function for it, perhaps funerary or cultic, rather than simply a water reservoir.