Stumholmen is a small island to the east of Trossö in Karlskrona, Sweden. It is connected to the center of Karlskrona by the Bastionsgatan bridge. Formerly the property of the Navy, today it houses the National Naval Museum (Marinmuseum), one of Sweden's oldest founded in 1752, the Hyper Island educational complex, and several other historic buildings. The unusual Slup- och barkass- skjulet is noted for its remarkable roof while buildings on Laboratorieholmen once served as an isolation hospital when the town was struck with disease. Comprehensive restoration and renovation work has been undertaken since the 1990s, providing a variety of interesting sights for tourists as well as residential accommodation for senior citizens. Since 1998, the Naval City of Karlskrona, of which Stumholmen is a key component, has been a UNESCO World Heritage Site.