The remains of the castle are mainly from the 15th–16th centuries, but the site is believed to have been an early fortress of the Dark Ages. Because of its strategic location, overlooking the shipping lanes, the castle played and important role in Scotland's history.

Surrounded by 160 feet high cliffs, the fortress is one of the most impenetrable in Scotland. It had only two access ways, one through the strongly defended main gate and the second was through a cave on the north side of the rock and then up the cliff, leading to the back gate, which was also well defended.

The ruins are spread over 1.2 hectares and are visited every year by hundreds of thousands of tourists.