DORA has been used as a concert venue. Kristiansten Fortress, built 1681–1684, is located on a hill east of Trondheim. It repelled the invading Swedes in 1718, but was decommissioned in 1816 by Crown Prince Regent Charles John. A statue of Olav Tryggvason, the founder of Trondheim, is located in the city's central square, mounted on top of an obelisk. The statue base is also a sun dial, but it is calibrated to UTC+1 so that the reading is inaccurate by one hour in the summer. The islet Munkholmen is a popular tourist attraction and recreation site. The islet has served as a place of execution, a monastery, a fortress, prison, and a Second World War anti-aircraft gun station. Stiftsgården is the royal residence in Trondheim, originally constructed in 1774 by Cecilie Christine Schøller. At 140 rooms constituting , it is possibly the largest wooden building in Northern Europe and has been used by royals and their guests since 1800. A statue of Leif Ericson is located at the seaside, close to the old Customs Building, the cruise ship facilities and the new swimming hall. The statue is a replica, the original being located at a Seattle marina. Nidaros Cathedral The Nidaros Cathedral and the Archbishop's Palace are located side by side in the middle of the city centre. The cathedral, built from 1070 on, is the most important Gothic monument in Norway and was Northern Europe's most important Christian pilgrimage site during the Middle Ages, with pilgrimage routes leading to it from Oslo in southern Norway and from the Jämtland and Värmland regions of Sweden. Today, it is the northernmost medieval cathedral in the world, and the second-largest in Scandinavia. During the Middle Ages, and again after independence was restored in 1814, the Nidaros Cathedral was the coronation church of the Norwegian kings. King Haakon VII was the last monarch to be crowned there, in 1906. Starting with King Olav V in 1957, coronation was replaced by consecration. In 1991, the present King Harald V and Queen Sonja were consecrated in the cathedral. On 24 May 2002, their daughter Princess Märtha Louise married the writer Ari Behn in the cathedral. The Pilgrim's Route (Pilegrimsleden) to the site of Saint Olufs's tomb at Nidaros Cathedral, has recently been re-instated. Also known as St. Olav's Way, (Sankt Olavs vei), the main route, which is approximately long, starts in Oslo and heads