Rock Castle, Berne Road, Portstewart, Co. Londonderry, BT55 7PB

Rock Castle was a late Georgian house built around 1820 by Henry O'Hara, located at Berne Road in Portstewart. It comprised a two-storey rendered structure with a three-bay central block, a segmental-ended porch, and circular drum towers flanking either side. The building had a pitched roof with plain parapets and Georgian-glazed four-pane windows.

The house was shown on the first edition Ordnance Survey map of 1830 and described in the Ordnance Survey Memoirs of 1835 as a bathing residence usually let during the summer months. According to those memoirs, it derived "its name from the style of its architecture, in which little taste is displayed". In summer 1835, the house was rented to J R White of White Hall, Ballymena, and his wife. Their son George was born at Rock Castle on 6 July 1835. George White later became a Field Marshal, was awarded the Victoria Cross during the Afghan Wars in 1880, and earned recognition as the defender of Ladysmith during the Boer War. He visited Coleraine in June 1900 to considerable public acclaim.

By the second edition Ordnance Survey map of 1856, the building was captioned 'Low Rock Castle'. Griffith's Valuation (1856–64) assessed it at £12, though it required repair at that time. In 1885 it was sold to Thomas Mackey, a wine merchant of Coleraine. At that date the house comprised 23 rooms including three reception rooms, nine bedrooms, kitchen, pantries, and two water closets, with extensive outbuildings comprising a large coachhouse, stable, byre, and coachman's house set on an acre of ground.

The property passed to James Leslie around 1920 and to the Wilsons in the 1930s. It was operated as a summer boarding house accommodating approximately 30 guests, with a rear return containing dining room, pantry and scullery, and a stable block to the south converted into accommodation for staff and visitors. In 1945 Robina Young purchased the property for £3000 and completely modernised the interior, with part of the building serving to accommodate overflow visitors from the Strand Hotel. The house was demolished in 2001 without permission during the construction of a modern apartment block on the site.