It is obvious that the waves played havoc in the sea-arm of Loch Ailort, in the southern Highlands of Scotland. In its mouth lies the island of Eilean nan Gobhar, which is famous for two vitrified forts. These forts have the peculiarity that the boulders from which they are built, are fused by the application of intense heat, so that they are firmly glued together. Often pieces of stone are wrapped in a glassy, enamel-like layer. But it doesn't necessarily make the walls stronger. Combat damage is unlikely to be the cause, as the walls must have been exposed to carefully maintained fires, which were hot enough to cause such vitrification. Today, experts explain vitrified fortresses as the product of deliberate destruction, as an act of ritual closure after the capture of the site by a hostile force.