|Summary:||Oval water tank; east of the harbor, west of the Sanctuary of Hera Limenia, just north of the Hestiatorion.|
|Date:||ca. 420 BC|
Cistern length: 21. 4 m; cistern height floor to top of roof: 4.6 m; cistern capacity: ca. 300 cubic m; settling tank: ca. 2.8 m wide.
Long cistern with apses at either end having 10 piers. Steps on the west. On the east a separate apsidal settling tank with a circular basin, fed by a large channel or drain.
The stone slab drain which fed the cistern drew rain water from the Sanctuary of Hera Limenia, and begins at the site of a sacred pool in the sanctuary. The steps at the western end of the cistern indicate that water was drawn there to serve the needs of the Hestiatorion. The Double-apsidal Cistern was contemporary with, and probably built as a feature of the Hestiatorion.