The Monastery of Croustalenia is situated at a distance of 42 kilometers from Aghios Nicolaos at the West and 92 kilometers from Heraklion at the Southeast, beside the village of Aghios Constantinos, near the eastern entrance to the Lasithi plateau, at a height of more than 800 meters. It is built on a low hill, surrounded by impressive rocks and huge perennial holm oaks. According to the inscription it is dated back to 1241 (the first years of Venetian domination) and it is dedicated to the Assumption of Virgin Mary.

During the revolution of 1821, the Monastery took an active part to the revolt of Cretan people, under the leadership of the abbot Gervassios, who was a member of the Filiki Etairia. Due to these actions, the Monastery was occupied in 1823 by the Egyptian Chassan pasha, who plundered and totally destroyed it. The damage was so extensive that, it was only in 1862 that the monastery was restored and started to function again as a worship center.

During the revolution of 1866-1869, the Monastery was the seat of the Committee of the Revolution and served as a workshop of cartridges for the weapons. On the 29 th of May 1867 the Monastery along with the villages of the area were destroyed again by the Ottomans.

By the end of the Ottoman domination and during the early 20 th century, an elementary school for the children of the villages of the area was established in the monastery.

During the German occupation of the island (1941-1944), the monastery had been used as a camp of concentration of the captives, after all monks had been kicked out, as they helped and looked after the partisans of the area. It is worth mentioning that the abbot of the monastery, Ermolaos Cassapakis, was arrested twice for his participation to the National Resistance. During this period, the monastery suffered again several damages, both of the buildings and the area around them.