Tholos Ionic capital of the partly restored Philippeion at Olympia, Greece. The Philippeion in the Altis of Olympia was an Ionic circular memorial in limestone and marble, a tholos, A tholos in ancient Greek architecture, was a circular building with a conical or vaulted roof and with or without a peristyle, or surrounding colonnade. The Ionic capital is characterized by the use of volutes, a spiral, scroll-like ornament. The Ionic columns normally stand on a base which separates the shaft of the column from the stylobate or platform.