The island of Despotiko in the centre of the Aegean Sea occupies a prominent position in the Cycladic archaeology, due to the extended archaeological remains uncovered in the area of Mandra in the northeastern part of the island. The systematic excavation is still unveiling the long history of the site through the discovery of numerous buildings, including a rich temenos dedicated to Apollo, which flourished particularly during the second half of the sixth century BC. The present volume is the result of a long period of study and close collaboration between archaeologists, architects, engineers and geologists, and it is dedicated to Building A, a quite unique structure, consisting of five rooms, recognised as the "temple" and the "hestiatorion" of the temenos of Despotiko. The first chapters are dedicated to the building itself. The analysis of the architecture of the "temple" complex is combined with the presentation of the restoration project, completed in 2020 and the detailed discussion of the building's stone lithologies in relation to geoarchaeological data. More than 600 objects, mostly made of clay, but combined with others of metal, ivory and faience, were found deposited below the floor slabs of Room A1. These findings together with the accumulation of disturbed and discarded objects recovered inside and around the building, are presented in the next two chapters. They are discussed in relation to the stratigraphical sequence identified during the excavation. The numerous vases, a large percentage of which complete, comprise much of this deposition, and they span a long period of time from the Geometric to the Late Roman era with the majority dating to the seventh and sixth century BC. The rest of the contents of the deposition include iron weapons and agricultural implements, pieces of jewellery made of bronze and silver, ivory discs and buttons, dress ornaments mostly of bronze and ivory, a few clay female figurines, metal and faience vessels, beads of gold, amber, glass faience, and steatite, seals and scarabs. The objects from the "temple" complex - mostly votive dedications - provided the basis for approaching the identity of both the deities worshipped at the temenos and of the cult celebrants, as well as for reconstructing the cult activities operating at the site of Mandra especially during the Archaic period.