The Kvarntorp industrial area south of Kumla was a large alum-shale processing plant that operated from the 1940s through 1966, extracting oil from the rock during the wartime fuel shortage. When the plant closed it left a series of vast slag heaps — and one of them caught fire and has been burning slowly from the inside ever since. The heap now stands more than 100 metres high, smokes lightly at its vents, and is measurably warm underfoot in places.
Rather than fencing off this industrial ruin, the local authorities turned it into an open-air sculpture park. Artists have placed works throughout the landscape, the industrial structures have been partially preserved as architectural elements, and walking paths wind around and over the heaps. The result is a strange and compelling combination of industrial heritage, environmental oddity, and public art. In winter, the snow melts first on the hottest sections of the heap, creating visible patterns that map the underground combustion. It is one of the more unusual places in Sweden and well worth the short detour from Örebro.