Copenhagen is mostly flat, which makes it easy to cycle. Years ago, the city decided to build proper bike lanes - wide, separate paths next to the road, with their own kerbs to keep bikes safe from cars. Today there are more than 380 kilometres of bike paths across the city. That is roughly the distance from London to Manchester.
Even the traffic lights are timed for cyclists. If you ride at about 20 km/h along the main routes, the lights turn green just as you arrive - this is called the 'green wave'. You can cycle right across the city barely stopping. Some bike paths even have footrests at the lights so you don't have to put your foot on the ground.
All sorts of people cycle - tiny children, grandparents, builders carrying tools, parents with three kids in a big box on the front. Special bikes called 'cargo bikes' have a wooden box at the front where the children sit. About one in four families with two or more children has a cargo bike instead of a second car.
Cycling everywhere has changed Copenhagen. The air is cleaner. The streets are quieter. People say hello more often because they aren't shut inside cars. Many other cities around the world now send teams to Copenhagen to learn how to make their own streets more bike-friendly.