The first information recorded in documents about the fortress on the Stronghold Hill (Martinsberg, Schlossberg), dates back to 1529, when the town was preparing to reject an attack guided by the troops of the Moldavian ruler Petru Rareş.
At the middle of the XVIth century, after the installation of the military control of the Habsburgic Empire's troops in Transylvania, the Citadel acquires an increasingly important role within the defensive system of the town. Between the years 1553-1554, the works coordinated by the count of Arco, develops the older nucleus, against which he builds artillery towers. The defensive settings up of the first construction phases, such as the shooting windows with splayed embrasures, have been shattered by the subsequent interventions, with however the conservation the wooden defence galleries of the internal courtyard. 
In 1630, during the judge mayor Cristel Hirscher's administration, it was completed the construction of the external bastion-shaped stronghold in bricks.  At the middle of south-eastern curtain it has been set up the gate tower, endowed with black oil orifices and shooting windows in form of reversed keyhole in the upper part.
At the beginning of the XVIIIth century, the entire assembly is surrounded by ditched and embankments, new expansion works took place after 1773, when is added the hexagonal tower and the two-levels building's aisle, which encompasses partially the constructions of the „castle” in the middle of the assembly.  During the following centuries, the Citadel functioned as prison; after 1851 it was used concurrently as military barrack.  The Citadel was visited by the Emperor Joseph the IInd, in 1773 and 1783, and also by the imperial couple Francis I and Carolina, in 1817. 
Between 1955 and 1975 it functioned as warehouse of the State Archives, and starting from 1981, after a consistent restoration, it became a touristic complex with medieval peculiarity.