The most well known landmark of Östersund is the national romantic Östersund City Hall ("Östersunds rådhus"). It is 51 meters tall and contains 136 rooms. It is the greatest constructional symbol of the National Romantic architecture in Östersund. The city hall looks almost like a fortress and affiliates especially to the local art of Jämtland. The bell tower is of typical Jamtish design shaped like an onion, the local sculpture Olof Ahlberg (1876-1956) made most of the sculpture details and the ornaments are made from Jamtish limestone. Östersund City Hall was designed by Frans Bertil Wallberg (1862-1935) and was seen by contemporary colleagues as the best of modern Swedish architecture. The main part of the building is accentuated by a grand tower and a monumental stairway. It is accompanied by only one wing, the north wing, as the second, south wing, was torn down in the 1970s. A recently built landmark is "Arctura", named after Jämtland's provincial star Arcturus, a large hot water accumulator tank. Due to its appearance it is referred to as "Termosen" ("Thermos"). At night the 65 meter building is illuminated with various lights like sunrise and the Aurora Borealis. Lake Storsjön's shores have long been inhabited. Though the area where Östersund is situated was for a very long time Frösön's link to the east mainland. Frösön, the island of the Norse god Freyr, was originally the centre of the region and it was here the only inland Scandinavian hill fort, Mjälleborgen, was built around 300 AD. The ancient Scandinavian thing Jamtamót was held on this island, the christening of Jämtland begun here and it was here the World's northern-most raised runestone, Frösö Runestone, was risen. Plans regarding the foundation of a Swedish city or "köping" (market town, "Chipping") in Jämtland existed among governmental officials already after the previously Norwegian province was ceded from Denmark-Norway in 1645. Queen Christina demanded the establishment of a sconce on Andersön shortly after the province became Swedish, this sconce would together with Frösö sconce secure the Swedish control over Jämtland. Christina's intention was to locate the "Jamts' city" within this fortification.