Telemarksgalleriet and Lysbuen is part of the Rjukan–Notodden World Heritage Site. Located in mountains and river valleys, this commemorates the world’s first industrial production of mineral fertilizer in 1905, from nitrogen in the air using hydro-electric power developed by Norsk Hydro. This was a vital development when farmers needed fertilizer to help them feed a fast-growing world population. Telemarksgalleriet and the World Heritage Center in the company town of Notodden tell this story and show art exhibitions in a monumental industrial building of the early twentieth century. The art collection contains pictures from the Telemark region‘s golden era of hydropower development and industrialisation and a cross-section of Norwegian socially engaged art.