- The Georgian main range, Cardiff Castle, in mid C19th from Annals and Antiquities of the Counties and County Families of Wales, by Thomas Nicholas 1872, p.462
The grounds of Cardiff Castle have a long history of landscaping, going back to the medieval period. The grounds owe their present day appearance to late eighteenth-century landscaping by Lancelot ‘Capability’ Brown and late nineteenth-century alterations by the 3rd Marquis of Bute.
In 1766 John Stuart, heir to the 4th Earl (later 1st Marquess) of Bute, acquired the lands and the castle by marriage to Charlotte Jane Windsor (1746–1800), who inherited it through her grandmother Lady Charlotte Herbert’s family who had owned it since 1550. John was created Baron Cardiff of Cardiff Castle later that year. In 1778 the 4th Earl of Bute commissioned Capability Brown and architect Henry Holland (Brown's son-in-law) to modernise the castle and grounds. Holland altered the Tudor additions and built two new wings, incorporating the hall, in gothic style.
Brown undertook a limited amount of landscaping in the grounds. He cleared the interior by removing the buildings from the former outer bailey and by demolishing the cross wall. He stripped the ivy off the keep, cut down the trees growing on the motte, made the spiral walk and filled in the moat.
The layout was simple: a single gravel walk around the edge on two levels. On the north and east sides it was along the top of the ramparts, on the south and west at ground level. The remainder of the interior was a 'fine level lawn', described in 1804 as 'a smoothly mown-grass plat and a spiral path 'that thrice encircles the lofty mount'. In 1794 Robert Clutterbuck, an antiquary and topographer who lived at Cathays, near Cardiff, in 1790s, noted in his journal that the green walks of the castle 'owe their disposition to the celebrated Brown'. In 1797 Henry Wigstead in his book Tour to North and South Wales mentions 'a very fine gravel walk is raised all round the walls, which is a public promenade'. A map of 1824 shows a belt of trees around the edge of the interior.
A gothick summerhouse probably stood in the south-east corner of the castle ward, on top of the bank. It is shown in a painting by Paul Sandby published in 1775 but dating to 1773. This octagonal building is very similar to that at Rookwood Hospital, Cardiff, and some believe that the Cardiff Castle summerhouse was dismantled and re-erected in the grounds of Llandaff House (later the grounds of Rookwood Hospital), then owned by Thomas Edwards, steward to the castle estate. If this did happen, the date of removal is unknown as there are no images of the building at the castle after 1776, but the 1776 map of Llandaff House only mentions a 'Summer House', giving no details).
Further work was planned on the property, including a reported proposal to roof the keep in copper, insert new windows and turn it into an assembly room for dances, but these projects were cut short by John’s early death in 1794. His son, also John, inherited the castle and his grandfather title becoming 2nd Marquis of Bute in 1814. In 1825 he began a sequence of investments in the Cardiff Docks, an expensive programme of work that would enable Cardiff to become a major coal exporting port and transformed the value of the Butes' mining and land interests, making the family immensely wealthy and enabling the next generation to carry out further work.
The castle took on its present form after 1868 from the partnership of the 3rd Marquis of Bute (1847-1900) and his architect William Burges (1827-81). They transformed the castle, building the Clock Tower, and giving the interior its highly decorated gothic character. One of Burges’s additions is a fantastical sunken roof garden, reached through a bronze door dated 1876. The roof garden is a marble-lined rectangular court surrounded by covered walks with mosaic tiling and classical bronze columns. The garden is highly decorated, with a bronze fountain, bronze statue of the Virgin and tile-paintings. From the garden there are panoramic views, including Castell Coch to the north. Work continued on the castle in the same style after Burges's death.
In 1947 Cardiff Castle was given to the people of Cardiff and became a public park after 1947.