The most unusual of Utö's sights is the remains of Sweden’s oldest iron mine, which opened in 1150 but closed in 1879. The three pits are now flooded – the deepest is Nyköpingsgruvan (215m). They're an atmospheric and impressive sight. The mining museum (in a wooden cottage opposite the Värdshus hotel) keeps variable hours (roughly 11am to 3pm in summer), so check locally.
