The CopenPay initiative, which was tested on a smaller scale last year, "is about raising travellers' awareness about travelling more responsibly," Soren Tegen Pedersen, the head of the city's tourism board Wonderful Copenhagen, told AFP.

The emphasis of the initiative is on transport, a highly polluting sector.

Those who make climate-friendly and environmental choices, such as using bikes and picking up trash, will also be offered rebates at museums and tourist sites, as well as free yoga classes and vegetarian meals.

Ninety sites are participating in the campaign, including the National Museum and CopenHill, a synthetic ski slope.

The campaign, which opens on June 17 and lasts until late August, will be advertised on billboards around the city and social media.

Goboat, a hire service for electric motorboats powered by solar panels, said taking part in the initiative last year helped show its commitment to climate solutions.

"Last year, 500 people jumped at our offer of one hour of free boating in exchange for picking up trash in the waters of the port. We weren't even able to satisfy demand," company representative Mads Pilegaard Sander told AFP.

In 2024, 75,000 tourists took part in the city's one-month trial.

Bike rentals increased by 29 percent during the period, tonnes of trash were collected, and 98 percent of participants said they would recommend the initiative, the tourism board said.