Across from the treasuries stands the Tholos, a circular, marble structure. Twenty Doric columns topped the base of three steps. The metopes depicted the Battle of the Amazons and the Battle of the Centaurs, while Corinthian half-columns decorated the cella's interior.

The Tholos was built in the early 4th century, possibly by Theodoros of Phokaia. Three columns have been restored, along with replicas of the cornice, metopes, epistyle, triglyphs, and some of the guttering of the roof. While the purpose of the building is still unclear, some believe it was dedicated to time related deities.

Tholos Close-up of Tholos