Château de Châteaudun was built between the 12th and 16th centuries. The Count of Blois Thibaut V had the keep built around 1170. The Sainte-Chapelle was built between 1451 and 1493. The choir and the high chapel were built between 1451 and 1454, with the nave and the oratory between 1460 and 1464. Jehan de Dunois, the bâtard d'Orléans (Bastard of Orléans), built the west wing (the "aile Dunois") between 1459 and 1468. The bell tower was erected in 1493.
François I of Orléans-Longueville began construction of the north wing between 1469 and 1491. The upper floors were added by François II d'Orléans-Longueville and his descendants during the first quarter of the 16th century.
Today the castle includes a keep, a chapel (Sainte-Chapelle), the Dunois wing and the Longueville wing. Château de Châteaudun overlooks the Loir river. Perched on a limestone outcrop, it shows its origins as a 12th century fortress. Converted during the Renaissance into a comfortable residence, the main body of the building is roofed in the gothic style. It still has, notably, a finely carved staircase from this period. Renovated since the 1930s, the castle has been classed as a historic monument since 1918.
References:Rosenborg Palace was built in the period 1606-34 as Christian IV’s summerhouse just outside the ramparts of Copenhagen. Christian IV was very fond of the palace and often stayed at the castle when he resided in Copenhagen, and it was here that he died in 1648. After his death, the palace passed to his son King Frederik III, who together with his queen, Sophie Amalie, carried out several types of modernisation.
The last king who used the place as a residence was Frederik IV, and around 1720, Rosenborg was abandoned in favor of Frederiksborg Palace.Through the 1700s, considerable art treasures were collected at Rosenborg Castle, among other things items from the estates of deceased royalty and from Christiansborg after the fire there in 1794.
Soon the idea of a museum arose, and that was realised in 1833, which is The Royal Danish Collection’s official year of establishment.