The name BULVERKET originates from the old Swedish words “bul” meaning “log” ad “verk” which refers to something “that is built”. It is related to the English word “bulwark”, a “form of fortification”, as well as the Dutch “bolwerk” with the same meaning as the Swedish “bulverk”.
The BULVERKET is the remnants of a large wooden fortification or bulwark at LAKE TINGSTADE 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 820ft in diameter.
According to a 1989 archaeological 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 archaeological finds, at 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. The KRAMPMACKEN has subsequently made several journeys, following old Viking waterways, through Eastern Europe.
It is likely that the Bulverket has been with the local people for centuries, as 1000s of logs can be seen through the water on a calm day, and it is also considered the best place for “perch fishing” on the lake. However, there is no “oral lore” regarding its construction, purpose or fate. Al that remains is a saying used in the northern part of Gotland that concerns large amounts of smoke —— “There is smoke just like when Lake Tingstade burned” —— Swedish : Det ryker som nar Tingstade trask brann)
The Bulverket was first mentioned in written sources in 1868, when Swedish archaeologist Oscar Mortelius wrote that naturalist and teacher Dr. Lindstrom discovered poles in Lake Tingstade in 1866. One of the recommended ways of seeing the Bulverket is diving in winter, when the ice is smooth and clear and the lake is used for “tour skating”.
The Bulverket was built in the middle of Lake Tingstade, in the least accessible part of the lake. It has now collapsed and the logs are scattered over an area of 40,000sq.miles. The main part of the Bulverket consisted of 4 piers or square “caissons” made of logs. The piers (98-131ft) wide, formed a square platform, each side of which was 560ft, with an open, but sheltered, water area in the middle. The platform was aligned, so that each side faced one of the “cardinal directions”. On the platform were houses for people living on the Bulverket, as well as storage sheds, in the centre part were “landings” for “mooring” boats. It is estimated that about 200 ships, of the early Viking Age type, could be moored there.
The platform was enclosed by two “concentric circles” of poles (or timber piles) driven into the bottom of the lake. In some parts, this outer defence stood as high as 160ft from the platform. The entire construction was about 820ft in diameter. The “palisade” and the “platform” had openings in the northwest part of the construction to allow boats in and out. Analysis of vertical posts show that the water surface is at approximately the same height as when the Bulverket was built, but that the depth of the water has decreased due to sedimentation, which is 1.6-3.3ft on the site.
The Bulverket was not surveyed and built as a simple unit, but rather one “caissons” at a time. Some of these “caissons” were linked by making rectangular holes in the ends of the vertical logs, stacking the logs on top of each other and then driving a horizontal pole, about 7.9 x 3.9inches, through the holes. The caissons were approximately 13ft high and covered with a flooring that rested 3.3ft above the water.
Houses were built using different methods, such as post-and-plank, log house technique and palisade walls. Construction details, found at the site, indicates that the houses were approximately 9.8ft x 9.8ft. A total of about 25,000 logs, mostly pine, were used to build the Bulverket. This equals to 120acres of forest. Studies of the construction show that it was built in a relatively short time, perhaps no less than a year. This would have required about 100 men to work on the site. Given the amount of organization needed for such a project and the farms around Lake Tingstade could not spare all of their workers, for the construction, most of northern Gotland must have been involved in the work.
Although the reason for the construction of the Bulverket is unknown, such a heavily fortified construction, in the middle of a large lake, suggests a place of refuge. The concept of such a building has no equivalent on Gotland or western Scandinavia suggesting that it may have been influenced by Slavic or Baltic buildings. During the time of the Bulverket, Gotland came under the pressure from representatives of the new Christian religion, and there is a theory that the Bulverket was needed as a stand against the tide of religious colonization.
Because of Lake Tingstade’s natural sedimentation, the remains of Bulverket are well preserved and the underwater archaeological finds, from the site, are in very good condition. Even small juniper boughs, placed on the ice by the carpenters to mark the layout of the Bulverket during its construction, have been preserved. It is likely that the logs and timber were cut during the winter and transported on the ice to the Bulverket.
The Viking boat KRAMPMACKEN was reconstructed in 1979-1980, based on the Bulverket boat. One of the initiators, of the project, was archaeologist and director of the Gotland department of Swedish National heritage Board, Erik Nylen. It was named after the Gutnish word for the “Baltic Shrimp” ——– KRAMPMACK ——— since the shape of the boat resembled a “shrimp. The boat is 26.2ft x 6.6ft, has 6 oars and is manned by a crew of 11 people. While the hull is based on the Bulverket boat, the sail is patterned after sails depicted on Gotland’s “picture stones”. In 1983-1984, the KRAMPMACKEN sailed from Gotland, via the Vistula and Danube Rivers to the Black Sea and Istanbul. In 1995-1997, a journey was made following the Caucasus rivers all the way to Baku on the Caspian Sea. Following these expeditions, several other reconstructed Viking boats have made journeys on the rivers of eastern Europe.