The Castle of Vicari, the most important architectural element of the town, today in a state of ruins, stands on the fortress of Pizzo Sant'Angelo dominating the entire town.
It was probably built in the Roman period, but its current appearance it owes to the restructuring carried out by Manfredi di Chiaramonte in 1390.
During its history the building was mainly used as a fortress: in 1077 it was used as a base to launch attacks on the castle of Castronovo by Count Ruggero; in 1278 the castle of Vicari was numbered among the royal fortresses of Sicily; in 1282, the time of the battle of the Vespers, the minister of Carlo D'Angiò and Giovanni di S. Remigio found refuge in the castle.
Among the owners of the castle, the names of the Chiaramonte, Valguarnera, Talamanca, La Grua, Ventimiglia families stand out , Alliata... The last owners were the Bonannos, princes of Roccafiorita, who kept the property until the end of feudalism.
The castle was surrounded by walls with various towers. The representative area was located in the highest part of the cliff, dominated by the main tower. The remains of the crenelated walls, the tower of the mill and the Porta Fausa, and the remains of the cisterns are still visible today.
It is supposed that originally, probably during the early Christian period or at most in the Byzantine era, the castle had a vestibule at the entrance which was later transformed into the church of S. Maria del Boikos. This must have been surrounded to the west by crenellated walls, still visible today.