This is how the Castle Tre Kronor looked like more than 500 years ago. Visit the Museum Tre Kronor and learn more about its history.  When entering the museum you will go through a passage that used to be a fortification wall- 5 meter thick! Is it not amazing?

http://www.kungahuset.se/kungligaslotten/kungligaslottet/museumtrekronor.4.19ae4931022afdcff380004889.html