The citadel in Câlnic was built around the year 1270. It was equipped with a keep and a defensive wall, surrounded by a moat filled with water, with access possible only via a drawbridge. After the citadel was taken over by the Saxon settlers, it was expanded through a secondary fortified wall and a tower to the south. Provision rooms and dwellings were built inside the enclosure in order to withstand sieges but, unfortunately, these have not been preserved.

At the end of the 15th century, a small church hall with an apse was added to the fortress. In the mid-16th century, the moat was filled, and the drawbridge was replaced by a gatehouse with a portcullis. Currently, the site is managed by a foundation belonging to the University of Cluj.

Câlnic preserves one of the last residences of the Transylvanian nobles. Due to its exceptional value and significance, the citadel is now a UNESCO World Heritage site.

In the 13th century, the nobleman Chyl de Kelling (the German name of the settlement, derived from the name of the ruling family) built a tower in the village to mark his residence. Due to frequent Ottoman attacks, the tower was fortified and surrounded by a massive defensive wall.

The Chyl noble family were never in good relations with the other prominent residents of the settlement. As a result, in 1430, the last nobleman moved out and sold the fortress to the villagers. They used the citadel as a refuge in case of Ottoman attacks and built additional defensive systems and storage spaces. In 1658, attackers managed to destroy the village but the citadel remained unconquered.