Tantallon Castle in East Lothian

You're standing at Tantallon Castle, high on a clifftop on Scotland's east coast, a few kilometres from North Berwick. Start with that huge wall of red sandstone. That's really all this castle needed. Steep sea cliffs protect it on three sides, so the builders simply put one wall straight across the headland. It's over fifteen metres high, more than three and a half metres thick and about ninety metres long. Now turn towards the sea. That rocky island out there is the Bass Rock.