St Fagans Castle

A castle of the thirteenth century stood here before the present house, and by 1536 it lay in ruins. By 1563 the site had been sold to a Dr John Gibbon, and the new house was built either by Gibbon himself or by Nicholas Herbert, who bought the site from him in 1586. The medieval work has not vanished entirely: part of the D-shaped boundary fortifications remains, forming a wall around the present house. The mansion is known in Welsh as Castell Sain Ffagan.

In 1616 Sir Edward Lewis of The Van, Caerphilly, bought the house from the Herbert family in trust, under the strict condition that it remain in the senior male line of the Lewis family forever. The interior dates partly from that period and partly from after 1850.

A lead water cistern brought from Van, a historic home of the family, is cast in monumental form and bears the family arms surmounted by a crown, with richly modelled relief panels and the Latin inscription DEVENIENDO, "in the course of becoming". Such cisterns were functional and symbolic at once in the great houses of the early seventeenth century, reflecting wealth, lineage and continuity of occupation. One decorative panel is deliberately cast inverted — a device used in early-modern ornamental and heraldic work as a memento mori, symbolising the transience of worldly power beneath enduring lineage. Against the Lewis family's emphasis on stewardship and settlement, that inversion has been read as reinforcing the theme of DEVENIENDO itself: an estate and a line understood as unfolding across generations rather than fixed in a single moment. The cistern is Grade II* listed in its own right.

The estate passed to the Windsor-Clive family in 1833, when it was inherited by Lady Harriet Clive, later the 13th Baroness Windsor and wife of the Hon. Robert Clive. Lady Clive undertook much restoration work spanning several decades. The sequence of garden terraces was created in 1865–6 and extended in the early twentieth century.

During the First World War the house served as a convalescent hospital for soldiers, with a ward of forty beds set out in the banqueting hall. In 1947, under the will of Ivor Windsor-Clive, 2nd Earl of Plymouth, the castle and estate were given to the National Museum of Wales.

In 1951 Iorwerth Peate, keeper-in-charge for the castle, was allowed by the Hon. John Morgan to select thirty pieces of furniture from Tredegar House for the castle's period rooms; Morgan was disposing of the contents of Tredegar House following its sale in lieu of death duties. Buildings in the grounds house the former Welsh Folk Museum, now St Fagans National Museum of History.

The castle has been statutorily protected in the highest category, Grade I, since 1977, and is recognised as a National Monument of Wales; the surviving medieval fortifications carry the same Grade I listing. The gardens and grounds are designated Grade I on the Cadw/ICOMOS Register of Parks and Gardens of Special Historic Interest in Wales, and many of the garden structures are listed Grade II.