Arthur's Seat last erupted roughly 340 million years ago, during the Carboniferous period. What remains is a complex of hills formed from the eroded remnants of the volcanic system -- basalt lava flows, ash deposits, and the remnants of volcanic vents. The summit provides views across Edinburgh, the Firth of Forth, and the hills of Fife. Though it can be climbed from almost any direction, the easiest route ascends from the east above Dunsapie Loch. The name's origin is uncertain and probably has nothing to do with King Arthur. Traces of four prehistoric hill forts have been identified within the park, at Arthur's Seat, Salisbury Crags, Samson's Ribs, and Dunsapie Hill. Cultivation terraces on the eastern slopes suggest farming here in the distant past. The park contains three lochs: St Margaret's Loch, created in 1856 as part of Prince Albert's improvements; Dunsapie Loch; and Duddingston Loch.

Salisbury Crags are a series of 46-meter cliffs on a subsidiary spur west of Arthur's Seat. In a charter of 1128, they were described under an older Gaelic name: Creag nam Marbh -- the Crag of the Dead. The track running below them is called the Radical Road, paved in the aftermath of the Radical War of 1820 to provide jobs for unemployed weavers from western Scotland, at the suggestion of Walter Scott. The road's creation gave easy access to the rock face, which the official Keeper of the Royal Park, the 8th Earl of Haddington, promptly began quarrying around 1821, causing damage still visible today. The Radical Road was closed in 2018 after a major rockfall. The cliffs are formed from dolerite and columnar basalt, and Samson's Ribs -- a striking formation of columnar basalt elsewhere in the park -- demonstrate the same volcanic geology.

It was on the face of Salisbury Crags that James Hutton, the father of modern geology, studied the junction between sedimentary and igneous rock in the 1780s. What geologists now call Hutton's Section showed him that molten rock had been forced between older sedimentary layers -- evidence that the Earth was shaped by slow processes operating over immense stretches of time, not by a single act of Biblical creation. This observation, made within a royal park in the middle of Edinburgh, helped overturn centuries of accepted chronology and laid the foundation for modern geology. Dynamic Earth, the science centre devoted to the story of the planet, now sits at the foot of the crags where Hutton did his fieldwork.

At the eastern end of the park, near Meadowbank, stands a cairn of cemented boulders. On 17 October 1720, an unemployed surgeon named Nicol Muschat cut his wife Margaret Hall's throat at this spot. He was hanged in January 1721. For centuries, the cairn bore his name -- Mushat's Cairn -- the memorial carrying the killer's name rather than the victim's. Walter Scott wrote the cairn into The Heart of Midlothian, further embedding Muschat's name in the landscape. That changed in 2024, when campaigners including author Sara Sheridan and local historian Andy Arthur succeeded in having Ordnance Survey maps officially rename it Margaret Hall's Cairn. The cairn now honors the life cut short rather than the violence that ended it.

The park's most dramatic spectacle took place on 7 August 1860, when 21,000 Scottish volunteers paraded before Queen Victoria and Prince Albert. The lower slopes of Arthur's Seat formed a natural amphitheatre, and somewhere between 100,000 and 300,000 spectators crowded in -- considerably more than Edinburgh's entire population, since many volunteers had brought their families from across Scotland. The march past took almost two hours. When the unified general salute was followed by three cheers for the Queen, the crowd joined in and the resulting volume spooked the officers' horses, causing temporary confusion. Prince Albert's reforms in 1844 had given the park its road network -- the circular Victoria Road, later called the Queen's Drive. Before that, no metalled road existed around the park at all.