By the 16th century, the castle's function shifted from military stronghold to noble residence. The Tudor period saw less warfare in the region, and the castle’s strategic role diminished.

In the 17th century, during the English Civil War (1642–1651), Cardiff Castle was again involved in conflict. It was held by Royalist forces loyal to King Charles I but was besieged and captured by Parliamentary troops. After the war, the castle fell into some disrepair as its military relevance waned.

The castle's architecture reflected this transition from fortress to home. Parts of the medieval structure were adapted for comfort, and gardens were developed. The castle began to embody the status and wealth of its owners rather than purely defensive purposes.

The Bute Family and Victorian Transformation

The most dramatic chapter in the history of Cardiff Castle began in the 18th and 19th centuries, when it came into the possession of the wealthy Bute family. The Butes were one of the richest families in Britain, with vast estates and commercial interests, especially in coal mining and shipping.

In 1766, the castle was inherited by John Stuart, 1st Marquess of Bute, whose descendants were determined to restore and transform the castle into a grand residence reflecting their status and taste.

The major transformation came under the 3rd Marquess of Bute, John Crichton-Stuart (1847–1900), who employed the renowned architect William Burges to renovate and redesign the castle extensively from the 1860s onwards.

William Burges was a leading figure of the Gothic Revival movement, known for his imaginative and lavish style. Under his direction, Cardiff Castle became a masterpiece of Victorian Gothic architecture and decoration.

Burges added new towers, lavish interiors, and elaborate decoration that blended medieval inspiration with Victorian romanticism. The interiors are richly painted, carved, and furnished, with themes drawn from mythology, history, and literature.

Among the most notable additions are the Clock Tower and the Arab Room, showcasing intricate designs and sumptuous materials. The castle grounds were also landscaped with formal gardens and parkland, turning the site into a cultural landmark. shutdown123