Castle Of St John

The Castle of St John, also known as Stranraer Castle, is an early 16th-century L-plan tower house in the centre of Stranraer, in Dumfries and Galloway, southwest Scotland. It was built by the Adairs of Kilhilt c.1510. It has been used as a home, a court, a police station and as a military garrison during the "Killing Times" of Covenanter persecution in the 1680s. During the Victorian era, the castle was modified to serve as a prison, and it was used as an ARP base during the Second World War. The castle was refurbished in the late 1980s and is now a museum.

Source: Wikipedia