Rosslyn Castle is an early 14th century stone peel and courtyard fortress, founded by Sir William St Clair, prince of Orkney. Standing on a rocky promontory which was breached on the north side to form a defensive ditch, a loop of the River North Esk, protects the other three sides. In 1390, Henry Sinclair, earl of Orkney added the great south-western donjon but in 1452 parts of the castle were accidentally damaged by fire. In 1544 during the English 'Rough Wooing' invasion, the castle was destroyed by troops under the Earl of Hertford, only to be rebuilt again in the late 16th century. Adjoining the square peel tower which flanks the south-east angle, a rectangular five storey east range with three lower vaulted service floors, was cut into the side of the rock. The gatehouse and north range were rebuilt and a permanent stone bridge replaced the drawbridge but in 1650 the castle was subjected to the artillery of Cromwell's commander in Scotland, General Monck. Further damaged by a Reforming mob in 1688, the older fortifications only survive as ruins but the upper two storeys of the east range have been restored. Guarding the approach, are the remains of the gatehouse and north range, with a section of high 15th century curtain wall on the western side. Of six bays divided by outer rounded buttresses, one bay serves as a postern gate, the outer wall of the keep, with its machicolated parapet also remains. The mound in the courtyard, beneath the keep, is formed from the collapsed remains of its other walls. 2 miles south-west is Old Woodhouselee Castle and 3 miles east is Dalhousie Castle.