Built between 1636 and 1637 by John Leslie, Bishop of Raphoe, this formidable structure cost £3,500 to construct; a princely sum partly offset by the strategic leasing of church lands. Leslie himself referred to his new home as ‘Raphoe Castle’, and with good reason: the building was designed as much for defence as for comfort, featuring a central four-storey block flanked by four distinctive salient-angled bastion towers at each corner. The foundation stone, still visible in the basement window of the northeast tower, bears a Latin inscription recording the precise dates of construction, whilst Leslie’s family bible provides an even more detailed account, noting that they moved into their new residence on 14 December 1637.

The Palace’s defensive capabilities were put to the test during the Confederate Wars when it successfully held out against attack, though it eventually fell to Cromwellian forces in 1650. The building suffered burning at the hands of the Jacobites in 1688, but was subsequently repaired by Bishop Cairncross and his successors. The original 17th century structure featured gun-loops strategically placed to provide flanking fire along the main walls, whilst the towers contained fireplaces on their upper three storeys, combining military necessity with domestic comfort. The main entrance, located on the first floor of the east wall and protected by an adjacent gun-loop, was later embellished with an 18th century Gibbsian surround, one of many modifications made over the centuries.

Bishop William Bisset undertook significant alterations shortly after his appointment in 1822, re-roofing the building and adding crenellated parapets and corner turrets that gave it an even more castle-like appearance. These romantic Gothic Revival touches, including mock machicolations and dummy cross-shaped loops, were the Palace’s final architectural flourish before fire destroyed the building in 1838. Today, the ruins reveal layers of history in their fabric: original 17th century rubble walls with cut-stone windows, 18th century modifications including enlarged timber-framed windows, and Bisset’s 19th century castellations. Three armorial plaques remain built into the palace walls, including the Leslie coat of arms, whilst a fourth noted by antiquarian Beaufort in 1787 now resides in a garden on William Street in Raphoe, a fragment of episcopal grandeur transplanted to suburban domesticity.