350 million years ago the Castle Rock was an erupting volcano which stood on a wide river plain, close to a tropical sea. When the volcano activity stopped, the volcano was buried beneath kilometres of sand and mud.
During the Ice Age the old volcano was uncovered by the tremendous force of ice, sculpting the volcano's solid core dramatically against the landscape. Its stark shape was further emphasised by the hollow gouged around it by the ice. This hollow became a marshy valley to the north which formed the Nor Loch when its streams were dammed in 1450.
The crag of Castle Rock formed a natural defensive position which was built on from around 1125. In 1760 drainage of the Loch began. Later the railway was constructed and Princes Street Gardens laid out on the loch bed. The gardens have evolved ever since and work continues to conserve and enhance them for the benefit of present and future generations.
In 1818, the Crown Estate, as owners of the castle and the south gardens, agreed with the Princes Street Proprietors a long term, low rent lease to make the area available for public use. In 1876, the lease was transferred to the City.
The result combines the forces of nature and the work of man's hand a beautiful garden within a unique setting.