The coastal enclosure of the Spinalonga fortress has a perimeter estimated at around 1200 m and is preserved in relatively good condition. It has two large bastions on its southern side, Tiepolo and Donato. The curtain wall connecting them was built during the Cretan War (1645-1669). To the east, the fortification extends along the coastline and is formed by walls and the fortifications of the Scaramella semi-bastion and the Rangone redent. In the northeastern part of the islet, there was originally only a wooden bridge, which passed over the deep crevice formed by the rock there. During the period of the Cretan War, the enclosure is completed, and thus the wooden bridge is removed.

On the island's northeastern side is the imposing fortress of the Michiel demilune. The fortified zone extends to the northwest with a straight wall section founded on the ruins of the old fortification. On the western side, there are several fortifications, such as the Pierino and Genese flanks, the Bembo redent and the Carbonana corner.