Rising 330 feet above the plains outside the town of Kumla, Sweden, the Kvarntorp Pile is hard to miss. But there’s more to it than first meets the eye. What was once a heap of ashes left over from producing oil has today turned into a whimsical creative landscape.

A Pile of Art, an eclectic exhibit containing about 30 sculptures, is spread out atop the pile. It’s a strange collection of art, set atop an even stranger manmade hill.

The Kvarntorp Pile (Kvarntorpshögen in Swedish) is a result of World War II. It’s where the country processed shale to extract the oil needed to supply its military. Throughout the war, and continuing onward for a couple more decades, the ovens in the area produced the precious black gold the world still so desperately desires. They also produced some 23 million tons of ashes, which eventually grew in to a gigantic pile that towered over the surrounding landscape.

Today, many years after the oil extraction ended in 1966, steam can still be seen rising from the ground at the Kvarntorp Pile. The ashes put there had a temperature that averaged about 1100° F, and whatever combustible material that was still there continued to burn underground. Even now, temperatures of up to 1300° F have been detected, though considerably lower temperatures are more common. Luckily, there isn’t anything to worry about—the steam is mainly just water vapor, and it’s risk-free to inhale. The scattered “No Entry” signs should, however, be adhered to since sinkholes do appear in some areas.

A Pile of Art opened in 1998, and new additions are typically added each year. During the summer, concerts and theatrical performances are held near the sculpture park.