Temple of Kronos and Rhea
From Project Athinai
In the 5th century BC, a poros temple dedicated to Kronos and Rhea already existed to the south of the Olympieion near the Diomeian Gate. However, this temple and its precinct have been completely replaced by a newer temple around 150 AD. A block of the cornice is the only finding related to the original temple. We can assume that the limits of the precinct of the original temple were the same as those of the latter temple, with the entrance of the precinct located on the north side. Unfortunately, everything else related to the original temple has been lost.
Travlos, John, Pictorial dictionary of Ancient Athens, Books that matter, New York, 1971, p. 335