No, this isn’t the world’s biggest bicycle graveyard. These bikes—thousands of them, owned by a bike sharing company—were recently pulled off the streets of Beijing, China’s capital, for repairs. China’s in the midst of a bike-sharing craze. It already has the world’s largest fleet of shareable bikes, topping more than 1 million (the U.S. has the third-largest, about 40,000), and bike sharing companies are making it easier than ever for China’s 1.3 billion people to get on two wheels. Riders unlock bikes using an app and rent them for about 1 yuan ($0.15) per hour; with no docking stations like in the U.S., riders drop them anywhere. But on China’s congested streets the bikes often get damaged and are simply abandoned. Bike-sharing’s popularity has been spurred not only by overcrowding but also by pollution problems—Beijing, for instance, has terrible smog. In some cases, bikes are becoming more popular than public transportation. “Right now, we are transporting more people than taxis in China in many cities,” Davis Wang, CEO of bike sharing company Mobike, told Fortune. “And in some cities . . . we are transporting more people than the subway.”