Carreg Cennen Castle

On the edge of Brecon Beacons National Park, about 30 miles west of Brecon, this decaying cliff-top fortress was built in the 12th century, and remains of earlier defenses have been found dating back to the Iron Age. The castle, though a ruin, has a partially intact barbican (fortified outer section) and some inner chambers hewn dramatically from the bedrock. The climb up is somewhat punishing—you have to trudge up a steep, grassy hill—but the views of the valley, with its patchwork of green fields framed by the peaks of the Black Mountains, are enough to take away whatever breath you have left. £4. Apr.–Oct., daily 9:30–6:30; Nov.–Mar., daily 9:30–4; last admission 45 min before closing.