Rhuddlan Castle (Cadw)

King Edward I liked his castles to be on the coast. It was safer that way. If his ruthless campaign to subdue the Welsh ran into trouble, supplies could still get through by sea.

At Rhuddlan, several miles inland, the plan was to use a river instead. Just one problem – the meandering Clwyd wasn’t quite in the right place. So Edward conscripted hundreds of ditch-diggers to deepen and divert its course.

More than seven centuries later Rhuddlan still looks like a castle that was worth moving a river for. Begun in 1277 it was the first of the revolutionary concentric, or ‘walls within walls’, castles designed by master architect James of St George.

Most impressive was the inner diamond-shaped stronghold with its twin-towered gatehouses. This sat inside a ring of lower turreted walls. Further beyond was a deep dry moat linked to the River Clwyd.

This bristling statement of Edwardian intent guarded a new town surrounded by ditched defences. You can still clearly make out the medieval grid layout of the streets in modern-day Rhuddlan.