Cardiff Castle is an unusual blend of Roman fort, medieval castle and fanciful Victorian gothic mansion.

The Romans established a fort on the site in the 1st century AD, but the square 8 acre fort that remains today was built in the 4th century. When the Normans built their castle in the late 11th century what remained of the Roman walls was buried under earth ramparts. The walls were revealed during excavations in 1889, and were rebuilt on the original foundations - clearly visible in places - between 1922 and 1925.

The Norman motte had a stone shell keep added in the 12th century. Further reinforcements were added by the De Clare family in the 13th and early 14th centuries. The keep gained a gatehouse and fore-buildings linked by a massive ward wall to a new tower in the south - the Black Tower. The wall and the keep's fore-buildings were demolished by 'Capability' Brown in the 1770's during re-development of the site. The moat that surrounded the motte was also filled in, but has since been restored and modern stone now marks the position of the old wall and fore-buildings.

In 1423, Richard Beauchamp, Earl of Warwick, built a new tower and hall block on the western wall of the site. This was improved in the late 16th century by the Herbert family who converted it into a luxurious and well appointed house. For most of the 17th and 18th centuries the house was left empty and fell into disrepair. In 1766 the house came into the possession of Lord Mountstuart, the future 1st Marquess of Bute. He began a programme of demolition and re-building that was continued by his grandson, the 2nd Marquess.

The 2nd Marquess of Bute gained immense wealth through the exploitation of mineral resources on his Glamorgan estates and his development of Cardiff as a centre for industrial trade. When he died suddenly in 1848 he left an infant son, John Patrick Crichton Stuart, as "the richest baby in Britain". The 3rd Marquess was to become one of the richest men in the world, and he lavished money on building projects at many of his properties. In 1869 work began to remodel Cardiff Castle to the designs of the Gothic Revival architect William Burges. The great wealth of Lord Bute provided Burges with the freedom to design and build his most fanciful schemes. A visit to Cardiff Castle without viewing the interiors would mean missing out on some of the most remarkable rooms ever created during the Victorian era. To fully appreciate the work of William Burges it is worth visiting nearby Castell Coch which was rebuilt as a summer retreat for Lord Bute and features more of Burges' gothic fantasy creations.