A large number of sports clubs are based in the city. During the Communist era, most sports clubs concentrated on all-round sporting development, therefore CSKA, Levski, Lokomotiv and Slavia are dominant not only in football, but in many other team sports as well. Basketball and volleyball also have strong traditions in Sofia. A notable local basketball team is twice European Champions Cup finalist Lukoil Akademik. The Bulgarian Volleyball Federation is the world's second-oldest, and it was an exhibition tournament organised by the BVF in Sofia that convinced the International Olympic Committee to include volleyball as an olympic sport in 1957. Tennis is increasingly popular in the city. There are some ten tennis court complexes within the city including the one founded by former WTA top-five athlete Magdalena Maleeva.