The Kastellos Tzermiadhon is a bold bluff which runs out from the slopes of Psarokorphe about ten minutes east of the village. It rises to a height of about 320 ft. above the plain. To west, east, and south the sides are fairly precipitous, but to the north it is connected with the cliffs behind by a kind of causeway, from the end of which a steep path reaches the summit.
It can never have been of strategic importance. It dominates one route into the plain of Lasithi—that from Potamoi via Zarams —but that was never an important route. Its nearest water supply is, to-day, at the wells called Pigaidhakia, which lie behind the Trapeza Plateau. It did however, in early times offer a safe habitation, well above the then marshy plain, and easily defensible in case of need.