CopenHill

Visible from around the city, CopenHill (aka Amager Bakke) is an undeniably creative – but equally controversial – monument to Copenhagen's sustainable ambitions. This architectural feat was designed by Bjarke Ingels Group, who won a competition about how to use the rooftop of this waste-management plant. BIG's audacious solution was this 450m green-roof ski slope, plus the world’s tallest climbing wall at 85m. Guests can rent skiing equipment, but most do with the long walk up to the rooftop bar. Take the lift down to see inside the energy source for 90,000 households. The climbing wall is as tall as the building, and though the ski slope may be made of green plastic, there are lifts, slaloms and ski rental at the ready. Views from the cafe-bar are unassailable. It’s free to walk the 450m to the top.