Cyclo-cross is a form of bicycle racing. Races take place typically in the autumn and winter (the international or "World Cup" season is September-January), and consists of many laps of a short (2.5–3.5  km or 1.5–2  mile) course featuring pavement, wooded trails, grass, steep hills and obstacles requiring the rider to quickly dismount, carry the bike whilst navigating the obstruction and remount in one motion. Races for senior categories are generally between 30 minutes and an hour long, with the distance varying depending on the ground conditions.