The only problem about this museum is finding it. We knew it was under the (not particularly impressive) Parliament building, but you can still spend some time looking and local shopkeepers possibly get fed up with being asked because they were remarkably unhelpful. We had given up and were walking back to the city center when we suddenly came upon the entrance! To avoid all this inconvenience go to the far end of the Parliament building from where you face it from near the central stations (right hand end if looking from the old town). It's down steps from the bridge between the Gamla Stat (old town) and the main center at that end - and when you go that way you may wonder how anybody could think it hard to find!
During the 70s, excavation for a carpark revealed some striking remains so the museum was built instead of the car park. The museum consists of these remains, brilliantly explained by maps and models. Modern brickwork is used to explain medieval building tecniques.
All sorts of modern work help to illustrate the way of life of medieval times as well, both residential and employment. The harbor simulation and the remains of a 15th century ship are particularly evocative.