The treasury of the Sicyonians was built in the second half of the 6th century B.C, replacing two former monuments, namely the tholos and the monopteros, which were considered to be ex-votos of the first half of the 6th century B.C. and are related to the victorious presence in the First Sacred War of the tyrant of Sicyon, Cleisthenes.

The treasury of the Sicyonians consists of three different buildings. Τwo of them date in the 6th century B.C. and the last one in the second half of the 6th century.  
Α. The tholos was probably the oldest building of this group, dating to ca. 580 B.C. It is attributed to the tyrant of Sicyon Cleisthenes, who was actively involved in the First Sacred War. Its diameter was 6.3 meters at the base and 3.54 meters in width. It had a colonnade which consisted of 13 Doric columns.  The cella, also circular, was built with ashlar masonry and had one door. The walls were 4.04 meters high. Nothing is preserved of its roof.  
 Β.  Τhe monopteros measured 4x5 meters and its 14 columns, monolithic, 2.78 meters high, supported the roof directly, without any intervening walls, a feature due to which the term "monopteros" is used.  The frieze of the architrave was decorated with scenes in relief, inspired by heroic themes, dating around 560 B.C. The entire construction reminds of a shelter for a precious and fragile ex-voto. It has been suggested that the monopteros sheltered the chariot with which Cleisthenes won the chariot race in the first Pythian Games of 582 BC. 
C. The actual treasury was a Doric building, distyle in antis, with vestibule and cella, measuring 8.27 x 6.24 meters. Its base was made of poros stone, quarried in the region between Corinth and Sicyon. It had the same orientation as the nearby Treasury of Siphnos, probably built at the same time (ca. 525 B.C.). The monument was built at a prominent spot, visible from the entrance to the sanctuary of Apollo. In its foundations architectural members from the two former buildings were embedded. According to the prevalent scholarly view, the Treasury was built by the citizens of Sicyon who forced Cleisthenes and his family demise from power. For its construction, material from the two earlier buildings, which were deliberately destroyed, was used.  

Text - Translation: Dr. Aphrodite Kamara, Historian