Tryvannstårnet is a 118 metre tall broadcasting tower of Oslo, located 529 metres above mean sea level at the hill Tryvannshøyden near the Tryvann lake.
Tryvannstårnet was built in 1962 and has an observation deck in a height of 60 metres, from which, weather conditions permitting, the sight extends to the Swedish border and the Gaustatoppen mountain. The observation deck was closed in 2005 because of new fire safety regulations that would have required expensive investments, as well as a rapidly declining number of visitors. In the 1980s and 1990s, the tower yearly had around 100,000 visitors, while in the last year it was open the number was only about 25,000.
At the basement of Tryvannstårnet, there is a large underground shelter.