A second day in Cardiff to explore the immediate vicinity.
First to Caerphilly (sounds like carefully) with the largest castle in Wales (!). The first was destroyed by the Welsh in the 12th century so the Normans took no chances the second time around: they diverted a river, built dams for a moat and a lake and made the first use of concentric walls. The Welsh never destroyed it again but it did take another Marquess of Bute to restore it.
From Caerphilly it was off to Caerleon by way of Newport. Both Caerleon and Newport had Norman forts but Caerleon’s claim to fame lies in the substantial Roman ruins, including fortifications, amphitheater and baths.