Edinburgh Castle dominates the skyline around Edinburgh, Scotland. It is built on a rocky crag above the city. On the seaward side is a sheer drop into the Firth of Forth. Records date the castle from about 1076. Seen from the land or sea, the fortress looks almost impregnable. From inside, the siege gun, Mons Meg, reinforces that impression. The gun, which dates from about 1450, fired balls weighing over 300 pounds.