p.mathias has added a photograph to the pool:
Edinburgh Citadel is a historic fortress which dominates the skyline of town of Edinburgh, Scotland, from its place on the Citadel Rock. Archaeologists have established human occupation of the rock since at the least the Iron Age (2nd century AD), though the character of the early settlement is unclear. There was a royal fortress on the rock since at the least the reign of David I within the 12th century, and the positioning continued to be a royal residence till 1633. From the 15th century the fortress’s residential function declined, and by the 17th century it was principally used as army barracks with a big garrison.