The cliff face of Salisbury Crags looks down on Edinburgh like a grand fortress. Situated in Holyrood Park, less than a half-mile (1 km) southeast of Princes Street, the Crags represent the glaciated remains of a Carboniferous sill, injected between sedimentary rocks which formed in a shallow sea some 340 million years ago. Glaciers sweeping outwards from the centre of Scotland have left a classic crag-and-tail, descending gently towards Arthur's Seat and Whinny Hill in the East. Salisbury Crags are of great significance in the development of modern geology. At Hutton's Section, the Edinburgh geologist James Hutton (1726-97) recognised that the rock now forming the Crags had been injected in a molten state. He was able to use this evidence to disprove the suggestion of the influential German, Abraham Werner, that all rocks had crystallised from a supposed primordial sea.
The Radical Road, which runs immediately below the Crags, was so-named after Sir Walter Scott promoted its creation to provide jobs for radical weavers from the West of Scotland. Subsequently, gentlemen of the Scottish Enlightenment would walk along the road to gain inspiration. Around the same time, the Earl of Haddington made himself unpopular by beginning quarrying operations on the Crags.