| Bulverket | |
|---|---|
| Native name Bulverket (Swedish) | |
| Bålverket, Tingstäde Bulverk | |
 Geologist Lennart von Post recovering part of the Bulverket in 1927. | |
| Type | Lake fortification |
| Location | Lake Tingstäde, Gotland, Sweden |
| Nearest city | Tingstäde |
| Coordinates | 57°43′40″N 18°37′43″E / 57.72778°N 18.62861°E |
| Area | 40,000 square metres (430,000 sq ft) |
| Elevation | 40 m (130 ft) |
| Original use | Unknown |
| Architectural style(s) | Viking wooden construction |
The Bulverket is the remnants of a large wooden fortification or bulwark at Lake Tingstäde on the island of Gotland, Sweden. When built, it consisted of a platform with houses surrounded by a double palisade with the entire construction around 250 m (820 ft) in diameter.
According to a 1989 archeological survey, the structure was built in the 1130s and may have been used for less than a century. Although its original purpose is unknown, theories suggest it was either used as a shelter during the turbulent times on Gotland at the end of the Viking Age or that it was the site of a last stand.
Among the archeological finds at the Bulverket are the remains of three boats. One of these served as a model for the reconstruction of a Viking boat, the Krampmacken, in 1980. Krampmacken has subsequently made several journeys following old Viking waterways through Eastern Europe.