A former prison has been converted into a far from grim property on this small, green island south of Kungsholmen. Run as a hotel in winter and youth hostel in summer, it has a pub (winter only), a café (summer only, in the former exercise yard) and a 17th-century Wärdshus serving Swedish cuisine. The yellow 19th-century building is still quite jail-like, with cells (yes, that's where you sleep) arranged around a light-filled central atrium. There's a prison museum on site (Långholmens Fängelsemuseum). One of Stockholm's most arresting places to stay.