The tholos had been constructed by the architect Theodoros originated from Phokis or maybe from Phocaea. It comprises features from various styles of ancient architecture. The outer peristyle has twenty Doric columns supporting a Doric freeze decorated with scenes presenting the battles of Centaurs and of the Amazons; the circular cella is also crowned with a Doric freeze of small metopes with relief decoration. Ten semi-columns in Corinthian style are found in the interior of the cella. The whole building stands on a three-stepped podium. The building creates a multi-color effect as several kinds of material have been used to the construction: Parian and Pentelic marble, bluish limestone from Eleusis and other. Only a few decorative features survive from the roof, as many of the decorative reliefs of the monument had been removed or disfigured by Christians. The shape of the roof is uncertain; the most prevalent theory is that it had a conic shape.
The monument was partially restored in 1938; several architectural parts, decorative sculptures and other features, also restored, are now displayed in the Delphi Museum.