Last week I was at Stockholm's Medieval Museum (⟶ Website). It is located under the bridge, which takes you from Norrmalm to the Royal Palace on Gamla Stan. The admission is free all the time. Since it takes only 30 to 45 minutes to walk through the exhibition, I decided to take that quick time travel into the dark ages. It was worth it! The museum fits perfect into every short stay in Stockholm and gives you a broad overview of the city's history and how it has developed in the mid-age.