The Mirabello province took its name after the homonym fort, located in the current site of Agios Nikolaos. There were more fortresses around, with the most important being that of Spinalonga, which protected the salt mines of Elounda, and some small castles in Kritsa, in Oxa mountain and, perhaps, in Kastelli of Fourni.
The fortress Castel Mirabello was first built probably the Genovese pirate Henry Pescatore, in 1206 (or earlier by the Byzantines) on the hill today housing the building of the Prefecture of Lassithi in Agios Nikolaos. The fort had almost square shape, with 4 towers on each corner and one taller on its north side. The Venetians, who threw out the Genoese, maintained the fort during the first year of the Venetian Era, in order to find shelter during the frequent revolutions and movements against them. But later, they abandoned it and used it as storage for the salt produced in the salt mines of Elounda (14th century), which was exported throughout Europe. In 1537 the Turkish pirates besieged the fort and destroyed. The Venetian Gio Vitturi then handed the fort over Michael Klontza, who restored it in accordance to the plans of the Venetian engineer Sammicheli. Concurrently, around the fortress a bourg started developing, which in 1583 had 753 inhabitants, mainly fishermen.
During the Cretan War, the Turks surrounded the fortress and the Venetian commander, Colonnello Baldella, surrendered immediately. For this treacherous act, the Venetians hung Baldella, and when they reoccupied the fort, they completely destroyed it, as they could no longer maintain it. Besides, the fortress of Spinalonga fully met the needs of the Venetians that time. Thus, the defenseless bourg was then abandoned till the revolution of 1866, when it began to get inhabited by the residents of Kritsa and gradually evolved to the current capital of Lassithi Prefecture, the town of Agios Nikolaos. From the fort there is nothing surviving, as the materials of the fortress were used to build the new settlement.
The fortress of Kritsa
West of the village Kritsa, near Agios Nikolaos, and very close to it there are the remains of an old fortress that locals call Kastellos. This was protected by very strong, double walls and was built on a steep hill. It is estimated that it was build during the second Byzantine Period (961-1206AD) or at the beginning of the Venetian Era.
The fort in Oxa
Near the lagoon of Elounda, there is a tall peaky mountain, named Oxa, in the top of which there are the ruins of a defensive construction. It seems that there was a fort that is now destroyed, in which the locals probably took refuge during the period of Arab rule and the pirate raids (7-8th century).