This is the most recent of all Castelli in Santorini, it was built around 1580. In the beginning, at its top there was a tower that was later demolished and the Monastery of St Georgios was built in its place. The walls of the houses composed the fortified surrounding wall of the castelli, while there was only one entrance.

The settlement was built upon a sequence of underground roads aimed at being used as a shelter in case the settlement would ever fall in the enemies’ hands. Once Skaros was abandoned, the Castelli of Pyrgos became the capital of the island.

Structure, Fortification & Buildings

The castle could be only entered at one point, the 'Porta', above which obtruded a square structure with an opening at the bottom part from which the inhabitants of the castle could pour burning oil on invaders. This structure no longer exists. Like all the other castles of Santorini, one can find a church close the entrance, in this instance, the church of Agia Theodosia.

Below the castle there used to be a system of passageways, used for protection or even escape in times of need. Within the castle walls, on the west side, one comes upon the church 'Theotokaki' or 'Koimisis of Theotokou' (Assumption), believed to have been built in the 10th century.

Also important is the Church of Eisodion of Theotokou, found at the highest point of the castle. It was built in 1660-1661, and on Easter Good Friday, the most important service of the Lamentations in Pyrgos is held there.

In the surrounding areas of Kasteli a new town has been built, which in the past was called 'Exoporta' or 'Outside Door' by the locals.