Perched on a rocky spur above the Our valley, Vianden Castle is one of the most beautiful and best-preserved medieval castles in Europe. Built between the 11th and 14th centuries, it fell into ruin over the following centuries before being meticulously restored from the 1970s onwards. The result is remarkable: a vast Romanesque and Gothic complex with a great hall, imperial gallery, chapel and panoramic views over the river and the village below. Victor Hugo lived in Vianden for a period and was so taken with the place that he sketched it repeatedly. Open year-round, and worth visiting in any season, but on a clear summer evening, with the valley lit up below, it's hard to beat.