- Built atop an extinct volcano: Castle Rock, the hill on which the castle sits, is the plug of an extinct volcano that last erupted over 340 million years ago.
- Hidden tower: David's Tower was built in the 14th century but collapsed during the Lang Siege of 1573. The tower ruins were buried beneath the Half Moon Battery, but they were rediscovered in 1912.
- Prison for American prisoners of war: During the American War of Independence, over 1,100 American prisoners were held captive in Edinburgh Castle. One prisoner, Ebeneezer Fox, carved a depiction of the American flag into the wall of his cell. This is believed to be the earliest known depiction of the Stars and Stripes outside of the United States.
- Said to be haunted: There are many different ghost stories associated with Edinburgh Castle, including the story of the headless drummer, the ghost of Mary Queen of Scots, and the ghost of a dog that was once thrown from the castle walls.