The treasury dedicated by the people of Siphnos was one of the most opulent monuments in the temenos of Apollo. Built near the beginning of the Sacred Way, next to the Treasury of the Sikyonians and opposite that of the Megarians, it housed the precious votive offerings dedicated by the Siphnians to the sanctuary.

According to Herodotus and Pausanias, Siphnos drew great wealth from its gold and silver mines and in the second half of the sixth century BC was the most prosperous of the Greek islands. The Siphnians decided to dedicate the tithe of their profits to Apollo and thus built the treasury. The monument's sculptural decoration is dated on stylistic grounds to 525 BC, or a little earlier, since that year Siphnos was looted by Samians in need of money.

The Siphnian Treasury is a small building in the shape of a temple, made entirely of expensive Parian marble, unlike most contemporary buildings, which were made of poros. Already in Herodotus's time it was renowned both for its unique beauty and its opulent sculptural decoration, which indeed is a masterpiece of late Archaic art. On the fa?ade, between the two antae, instead of columns, were two korai, exquisite examples of the Ionic art of this period. The architrave is decorated with an Ionic kymation and a frieze on all four sides. On the west side the frieze depicts the judgement of Paris, on the south the rape of the Leukippidai by the Dioskouroi, on the north and best preserved section of the frieze the Gigantomachy, and on the east, the main fa?ade, an assembly of Olympian gods watching the Trojan War. The robust expression, clarity of form, powerfulness of the figures and intricate detail serve the decorative character of the frieze, the sensitive arrangement and exploitation of the surface. The east pediment has retained its sculptures, which depict a favourite theme to both sculptors and vase painters in the late Archaic period, namely the dispute between Hercules and Apollo over the Delphic tripod. The pediment is crowned by three acroteria, the central one depicting a sphinx and the lateral ones a pair of Victories.

Of the Siphnian Treasury, only the foundations and one of the astragals decorating the base are in situ. The surviving sculptural decoration has been conserved and is displayed in the Delphi Archaeological Museum.