In a typical year, more than 45,000 spectators pass through the gates of the Ice Park home of the World Ice Art Championships. The competition is broken down into two main categories: Single Block and Multi-Block and each competition is further separated into Abstract and Realistic sculptures. One of the most popular attractions is the Kids Park where children of all ages can glide down ice slides or spin in ice twirly tops. Typically held the last week of February and the first week of March, spectators may view the sculptors at work during the championship competitions. In the Single Block Classic, teams of up to two persons work on a 3'×5'×8' (90 cm × 150 cm × 200 cm) block of naturally formed Alaskan ice, weighing roughly 7,800 pounds (3,500 kg). In the Multi-Block Classic, teams of up to four persons each receive ten blocks of approximately 6'×4'×3' (180 cm × 100 cm × 90 cm) each weighing about 4,400 pounds (2,000 kg). to create their crystal masterpieces. Teams that compete in both the Single Block and Multi-Block events must handle a total of 50,000 pounds (23 t) of ice. Power tools and scaffolding can be used in both events: assistance from heavy equipment is only permitted in the Multi-Block Classic Competition. Thus, participation in the event requires strength, endurance, and engineering skill as well as mastery of basic ice sculpture techniques and artistic vision. The National Ice Carving Association (NICA), based in Oak Brook, Illinois (in the Chicago metro area) is an organization of ice carvers and those interested in ice carving. NICA sanctions and supports various ice sculpture competitions around the United States and in Canada and has held a yearly National Championship since 1991. The association has developed a point system for judging the quality of ice sculptures created in timed competitions and certifies competition judges. NICA also was responsible for managing the ice carving competition held in conjunction with the 2002 Winter Olympics in Salt Lake City and provided support for the 2006 event in Italy. In 2007, NICA started a "Tour of Champions" that rewards high scores over several competitions, usually including the National Championships. In the city of Rio Cuarto, Cordoba since 2015 there is an Ice Festival call "Roca minus zero". The largest display of ice sculpting in the United Kingdom is the London Ice Sculpting Festival.