The fort Castel Belvedere or Kastelos was built on the isolated hill Kastellos, that was accessible only from its south side, near the villages of Ano and Kato Kastelliana. Here was the site of the ancient city Priansos, a powerful and great town that minted its own currency and had its seaport at Inatos (current Tsoutsouras).
The castle dominated the western edge of Messara and was built by the Genoese pirate Pescatore between 1206-1210. During building, materials were extracted by the ancient town Priansos, which was built at the same position. The name Belvedere means good view, derived from the stunning views towards all directions.
When the Venetians occupied Crete, the repaired the castle and added water tanks, barracks and the buildings of the local castellany. Belvedere Castellany consisted of the current province of Viannos and Monofatsi.
During the first centuries of the Venetian Era, when the natives rebelled frequently, the Venetians took refuge in the fortress. Since then, small settlements (bourgs) started forming near the fort, which later evolved to the village Castelliana. But when the revolutions seized, the fort lost its importance and was abandoned.
The fort hosted six churches, of which three survive (Assumption, Presentation of the Virgin Mary, St Anastasia). Here, near the church of Assumption there is the cave of Arapis (Neger), where the inhabitants took refuge when in danger.