In the Mylopotamos province, one of the most mountainous in Crete, there were many fortresses. Among them are the Castle of Mylopotamos located in the village of Panormos and Panokastri near Agios Mamas. Panokastri or Pano Kasteli is situated in a rocky position above the village Kastri. This belonged to the family of the noble Alexios Kallergis from 1341. The Kallergis family took part in the Apostasy of Saint Titus (1363-1366). This failed rebel was supported by the Venetian feudal and Cretan leaders, who tried to establish an independent democracy under the patronage of Saint Titus, patron saint of the island.
After the defection of the apostasy, the Kallergis family declared a new revolution, which quickly took on great dimensions. It was then that they fortified their feud in Kastri, building the fortress of Apano Kasteli. But this revolution was suppressed and the bases of the revolutionaries (Lassithi plateau, the area of Eleftherna and Anopolis Plateau) were evacuated for a century. Also, Kallergis feud was granted to Nicolao Delphyno, who later handed it to Lac de Medio.
Nowadays there are remains of the fortress, traces of the wall on the south side of the hill and the church of Panagia Panokastriani, where one can still see traces of the Kallergis coat of arms.