Edinburgh Castle is a historic fortress which dominates the skyline of the city of Edinburgh, Scotland from its position on the Castle Rock. Archaeologists have established human occupation of the rock since at least the Iron Age (2nd century AD), although the nature of the early settlement is unclear. There has been a royal castle on the rock since at least the reign of David I in the 12th century, and the site continued to be a royal residence until the Union of the Crowns in 1603.