The colossal Mons Meg gun points out from the ramparts of Edinburgh castle to Edinburgh New Town. One of a pair of "bombards" it was a gift from the Duke of Burgundy to King James II of scotland in 1453. The gun was last fired in 1681 to celebrate the birthday of James Duke of Albany and York, later King James II of England and VII of Scotland, when the barrel exploded and Mons Meg was retired for ceremonial use.
The 22" (56 cm) calibre cannon fired balls (right of the gun) weigh around 180 kg (396 lb). Mons Meg could fire up to a distance of 2 miles. However, the cannon could only be fired up to 10 times a day due to the excessive heat caused by the powder charge required.
This picture also shows how the inside of Edinburgh Castle was shaped around existing volcanic rock.