O Cebreiro

Deserted and haunting when it's not high season (and often fogged in or snowy to boot), O Cebreiro is a stark mountaintop hamlet built around a 9th-century church. Known for its round, thatched-roof stone huts called pallozas, the village has been perfectly preserved and is now an open-air museum showing what life was like in these mountains in the Middle Ages—indeed, up until a few decades ago. One hut is now a museum of the region's Celtic heritage. Higher up, at 3,648 feet, you can visit a rustic 9th-century sanctuary.