edinburgh12 The Edinburgh Castle A Natural Fortress One of the strongest sites in Scotland, the Castle Rock has been fortified since 1100 AD. Besieged many times, it was from this side that the Castle was most vulnerable. On the ground in front of you cannon were set up on several occasions to batter the Castle defenses. Supports of Mary Queen of Scots were besieged in the Castle in 1573. On May 29th after two weeks of continual bombardment, with many buildings destroyed and the defenses badly damaged, the Castle surrendered. The Governor of the Castle and three others were hanged then beheaded and their heads placed on the 'most eminent places of the castle wall'.