CopenHill

In the industrial neighborhood of Amager, CopenHill (known to locals as Amager Bakke) is the world's first combination re-usable energy power plant and fully functioning ski slope. Its boxy silver exterior, lean gray smoke-billowing towers, and blinking red lights are viewable from throughout Copenhagen, but at the top of the 85-meter climb to the hill's roof visitors will find a fully-operational dry slope for skiers and an observation look out with breathtaking views of the city.

A ski lift and elevators are also available to help you make the ascent, and walking paths along the edge of the building offer a path for fitness enthusiasts who lack a fear of heights. If that doesn't sound enough like spitting in the face of acrophobia, the world's highest climbing wall is currently being constructed along one of the building's tallest outside edges (it will be 85 meters tall by 10 meters wide and come directly off the side of the building) and is scheduled to open in spring 2020. Wisely, it will require certification to climb.

The building, which cost some $650 million to construct, was designed by Danish architecture firm BIG as a grand gesture towards reaching Denmark's goal of becoming the world's first carbon-neutral city by 2025. The firm is also responsible for designing Denmark's notoriously pink Superkilen, sci-fi sets for the show Westworld, and an enormous Tesla coil for a power station in London. The firm's CEO Bjarke Ingels has called CopenHill, "a crystal clear example of hedonistic sustainability" with the plant boasting the potential to generate enough clean energy to deliver electricity to 150,000 homes per year by incinerating 440,000 tons of waste.