Dumbarton Castle is situated on top of a volcanic plug of basalt in what was once the ancient capital of Scotland. Since the Iron Age, it's high twin peaks served as a natural fortress. It was besieged several times, the most destructive of which was by Vikings in 870.

It was subsequently reinforced with the building of a royal medieval castle but most of what remains today are artillery fortifications dating from the 1600s and 1700s.