Aberystwyth Castle in Ceredigion

You're standing at the ruins of Aberystwyth Castle, on the coast of Mid Wales. What's left today are pieces of walls and towers, but this was once one of the mightiest fortresses in the region. Take a look at the shape of it. The inner part was laid out like a diamond, with a tower at every corner. Around it ran a narrow outer ring. That's what's called a concentric castle: walls within walls. To the north there was once another enclosure, but the sea has swallowed it over the centuries.