The castle has had two main construction periods: the changes made by Bethlen Gábor in the early 17th century and the changes made by Zólyomi Dávidné in the mid-century. In 1618 the estate became the property of the Bethlen family de Iktár (now Ictar-Budinț). Bethlen Gábor changed the castle's appearance and strengthened the castle's exterior with fortification, and then, together with his estate donated it to his nephew, Bethlen István. After his nephew's death in 1632, the castle was lived for a short time by his nephew's wife, Széchy Mária. In 1648 the castle became the property of miss Zólyomi Dávidné, Bethlen Katalin. In 1685 one of its buildings was used as an “iron house”, meaning it served as an iron storage. Since 1725, the castle housed the Treasury agencies. The fortress was last used in 1784 for military purposes, when a large part of the county's nobility found protection here against the Revolt of Horea. When visiting the castle, in 1807, I.Francis ordered its renovation, but a disastrous fire caused by a lightning ended the works in 1818. After the War of Independence, the district offices functioned also in the castle. In 1854 another fire distroyed the castle. In 1868, after many decades of neglect, as a result of Arányi Lajos's campaign, the castle's renovation was initiated through donations. Originally the renewal of the castle was intended to be made for Archduke Rudolf, as a gift of the Hungarian nation. The reconstruction work was directed first by Schulcz Ferenc and then, in the period of 1870 – 1874, by Steindl Imre. In accordance with the style from that period, they consistently tried to “regive” the fortress a gothic style. Some parts were highlighted and other destroyed and replaced with new ones (these changes were partially corrected later). Steindl has given the roof  its present form. The castle's scientific related restoration can be linked to Möller István's name (1907 -1913). Since 1956 continuous restoration works are undertaken at the castle.

The entrance into the castle is made through a wooden bridge supported by four massive pillars, placed across a wide and deep moat. On the left side, facing the town, Bethlen has built the Knight's castle, which once housed the warehouse, premises and the shed of hunting dogs. The Gate Tower was built in the 1440's. Before this date, the entrance in the castle was made on the opposite side, through  the old gate tower placed at the southern corner of the courtyard. The Gate Tower allows the acces to the dungeon. On its western side there is the Palace Wing of the castle, which was built during the reign of Hunyadi János. The lower level of this wing houses the Knight's Hall, decorated by fresco. The upper level houses the so-called Parliament Hall, the name referring to the fact that in the time of Hunyadi, this was the place where the most important negotiations took place. Bethlen changed the former defense place between the Gate Tower and the Palace Wing into a “ladies house”. The external structure of the palace wing, with balconies and turrets, was designed due to the structures used for defensive purposes.  On the east side of the Gate Tower, the so-called Golden House is closed by the Buzdugan Tower (Mace Tower) and the Corvin János (John Corvin) bastion. After 1458, Szilágyi Erzsébet has added to the internal wall of the Golden House the Matthias Loggia: this is considered the first preserved Transylvanian renaissance architecture. The Loggia contains contemporary, late Gothic frescoes. The castle's chapel is located on the soth-western part of the Golden House. Originally it was built between 1442 and 1446, but Bethlen made significant changes to it. He pushed the vault aside, establishing an internal access with the Golden House. At the south-western side of the chapel, on a small courtyard, there is the castle's fountain, which the inscription of a Turkish prisoner, dated mid 16th century. The inscription in Turkish language, engraved in Arabic letters sounds as follows:"He who wrote it is Hassan, the gyaours prisoner in the fortress near the church." The eastern side of the castle is occupied by the Bethlen wing. At the restoration of the 19th century this was built for the Archduke Rudolf's personal purposes. Steindl's most significant interventions can be seen inside: the neo-Gothic loggia. The Painted Tower is located at the north-eastern corner of the wing. The entire south side of the castle is covered from the outside by a defensive bastion called White Tower. At the southwestern part there is the so-called King's House, which was built by Zólyomi Dávidné. From here, the acces to the Grand Palace is made trough the Staircase Tower and the Capistrano Tower. In case of siege, defenders could approach the Nebojsza Tower, located 35 meters away from the castle, by using the drawbridge from the Capistrano Tower .The Serbian name, Nebojsza, means: “Don't be afraid!”. The five-storey fortress built in Hunyadi's time was intended to be the last refuge for the case when the assailants penetrated into the castle. Machicolations lead to it.