CopenHill is the first power plant that incorporates a ski slope.
By incinerating waste to produce electricity and heat, the 4.4 million-square-foot power plant releases less carbon dioxide into the atmosphere than it would if it burned fossil fuels.
Copenhagen hopes to become the world's first zero-carbon capital city by 2025.
Some environmental groups say waste-to-energy plants still aren't exactly "clean," since burning waste emits carbon dioxide, as does transporting that waste to the plant. CopenHill also produces a lot less energy than fossil-fuel power plants.
But the trash the plant burns would otherwise end up in a landfill, where it could emit methane — a greenhouse gas that's up to 35 times as potent as carbon dioxide.
The plant burns 440,000 tons of waste per year — but skiers won't smell any of it.
Each day, CopenHill receives around 300 truckloads of waste from local households and businesses, along with waste that gets imported from other countries, including the UK.
The steam that comes out of the plant gets filtered for pollutants, including a greenhouse gas called nitrogen oxide. A garden on the roof is also designed to absorb particles that could linger in the air.
The plant's architect, Bjarke Ingels, officially opened the ski lift on October 4.
Ingels' firm, BIG (Bjarke Ingels Group), has been working on the project for nearly a decade.
"I have a 5-month-old son and he's going to grow up in a world not knowing there was a time when you couldn't ski on the roof of a power plant," Ingels joked at the TED 2019 conference in April.
He told Architectural Digest that he was inspired to design the slope after realizing that Copenhagen had "several months of snow, but absolutely no mountains."
Conveyor belts called "magic carpets" take skiers and snowboarders to the top of the hill.
Visitors have the option to bring their own ski gear or rent it on-site.
"It's a fantastic experience in the middle of a city to be able to do what you do like the most," local skier Pelle Hansen told Reuters in February. "Instead of having to go six, seven, eight or 10 hours to a ski destination, you can be here in 10 minutes."
A glass elevator allows visitors to peer inside the plant.
In addition to the waste-burning facility, the plant contains 10 floors of administrative space and a 6,500-square-foot education center for conferences and workshops.
The ski slope is made of neveplast, a synthetic turf that's slippery like snow.
"I think everybody is surprised to start with when they look at it and it's not snow," Christian Ingels, the director at CopenHill, told Reuters. "It's green dry-slope material. After one or two runs, your mind is automatically adjusting so you feel exactly like skiing."
Four ski runs offer varying degrees of difficulty.
There's also a freestyle park and a slalom course.
On the way down, skiers pass other amenities, including a rooftop bar, café, fitness area, and a walking trail.
The side of the plant boasts the world's tallest artificial climbing wall, which is nearly 280 feet high.
The plant's director hopes the facility will attract more than 300,000 visitors per year.
Around 65,000 of those visitors are expected to use the ski slope.
"As a power plant, CopenHill is so clean that we have been able to turn its building mass into the bedrock of the social life of the city," Ingels said at the slope's opening ceremony. "Its facade is climbable, its roof is hikeable, and its slopes are skiable."
