Cardiff Castle, castle located in Cardiff, Wales. A fortification has stood on the site since Roman times (see Roman Britain) but the current external appearance of the main structure is the result of major alterations that were carried out in the 19th century.

Robert FitzHamon, Lord of Gloucester, constructed an earth and timber fortification on the site of the earlier Roman structure in the 1090s. By 1150 the wooden fort had been replaced by a stone keep. The keep still stands today within the grounds of the later castle, which also house the Regimental Museum of the 1st Queen’s Dragoon Guards; part of the Roman wall is still visible within the grounds. The appearance of the main castle structure was completely altered for the 3rd Marquess of Bute by the architect William Burges in the 19th century, along romanticized medieval lines (see Gothic Revival). The main castle is today known particularly for its lavishly decorated interiors, also designed by Burges. The two men also collaborated on another structure, Castle Coch, which stands outside Cardiff.