The lovely Torre de Menagem (castle keep) stands alone on a grassy embankment behind Chaves' main square, the only major remnant of a 14th-century castle built by Dom Dinis. Around the tower are attractive manicured flowerbeds and a stretch of old defensive walls, with views over the town and countryside. For even better views, visit the Museu Militar, where a series of creaky staircases climbs past a motley collection of military gear to the tower's panoramic rooftop terrace.