Places like the Tap o' Noth look like the the ruins of any mysterious hill top fortress that we have quite a lot of in Scotland - its only when you look closer

Places like the Tap o' Noth look like the the ruins of any mysterious hill top fortress that we have quite a lot of in Scotland - its only when you look closer do you realise that the rubble is actually all stuck together by melted rock. The fort (or inner bastion as there was a large outer settlement) is 100m by 30m and the walls roughly 5m by 8m - which is a lot of rock!