In Copenhagen, the Danish capital that pledges to become the world’s first carbon-neutral city by 2025, a 410-foot tall smoke stack is a cause for celebration and the massive incinerator beneath it the latest tourist attraction.

Especially if you bring skis.

The Amager Bakke powerplant, designed by the Danish architect Bjarke Ingels, turns local trash by incineration into low-carbon energy. The process, as designed, is so clean that the facility’s roof has been created to be a recreational area. “CopenHill” opened October 4, with hiking trails, a fitness center, even an artificial ski slope on its slanted roof.

“Amager Bakke is the embodiment of how we want to combine sustainable thinking and innovative architecture with recreational facilities when developing the city,” said Frank Jensen, Copenhagen’s mayor, in an email.