This huge, awe-inspiring Neo-Norman castle was built in 1819-35 by Thomas Hopper for George Dawkins Pennant, whose great-uncle Richard Pennant had made a fortune from the slate mines of north-west Wales. It incorporates within it two earlier buildings: a medieval house and an 18th-century Gothick mansion. The exterior is a picturesque grouping of neo-Norman towers and battlements. There is a 115ft high keep containing the family apartments. The cavernous interiors are elaborately carved with abstract and figurative motifs adapted from medieval and Celtic sources. There are ornate ceilings, probably by Francesco Bernasconi, stained glass by Thomas Willement and early 19th-century Chinese wallpapers. Dawkins Pennant had no sons; his son-in-law Edward Gordon Douglas, created Baron Penrhyn of Llandegai in 1866, entertained both Queen Victoria (1859) and William Gladstone (1861) at the castle.