Mountain bike racing (shortened MTB or ATB racing) is a competitive cycle sport held on off-road terrain. The Union Cycliste Internationale (UCI) recognised the discipline relatively late in 1990, when it sanctioned the world championships in Purgatory, Colorado. The first mountain biking world cup series took place in 1991. Its nine-race circuit covered two continents—Europe and North America—and was sponsored by Grundig. In 1992, the Grundig-UCI world cup circuit expanded to ten races, and remained a trans-Atlantic series. Cross-country racing was the only world cup sport at this time, then in 1993 a six-event downhill world cup was introduced. In 1996, cross-country mountain biking events were added to the Olympic Games.