Founded in 1147, Margam Abbey is the only Cistercian monastery in Wales whose nave is still intact and used as a parish church. It’s also surrounded by plenty of relics of its past glories, notably the 12-sided chapter house. Just across the graveyard, the Stones Museum has a magnificent collection of carved stones and crosses, some dating from the 6^th century, alongside a splendidly rude gargoyle.