Södra Riddarholmshamnen (see marking at the map below)
GPS: 59.324072, 18.062736
Mälardrottningen is unique, it's a ship where your room is a cabin and your view over the City is absolutely fantastic. This is the Hotel of choice for people who want something different. The best part is that it's still very central located with only 10 minutes walk to the Royal Castle, the Subway station or the main shopping street.