Dovrefjell is a mountain range that forms a natural barrier between Eastern Norway and Trøndelag, the area around Trondheim. As a result, it has been heavily trafficked during and probably preceding historical times. Several mountain inns were established in the Middle Ages to house pilgrims traveling to Trondheim, and there are even ruins of an old leper colony in the northern area of it. The main south-north highway (E6) and railway Dovrebanen in Norway runs over Dovrefjell. The highway is a year-round highway but is at rare occasions closed for short periods during heavy winter weather conditions. The natural habitat for many rare plants and animals, it became a national park in several stages starting in 1911, when some plants were put under protection. When the railroad was built from Oslo to Trondheim in 1921, one of the marshes was preserved. In 1974, parts of the range became a national park and the park was extensively enlarged in 2002. Together with Rondane, it has Norway and Europe's last stock of wild reindeer of Beringian origin. Dovrefjell (west of E6/Dovrebanen) also has a stock of musk oxen, imported from East-Greenland in 1932.