The Australian Open is the first of the four Grand Slam tennis tournaments held each year. The tournament is held each January at Melbourne Park. The tournament was held for the first time in 1905 and was contested on grass from then up to 1987. Since 1988, the tournament has been held on hard courts at Melbourne Park. Mats Wilander is the only male player to have won the tournament on both grass and hard courts. Like all other Grand Slam tournaments, there are men's and women's singles competitions; men's, women's, and mixed doubles; and junior's and master's competitions. The two main courts used in the tournament are Rod Laver Arena and Hisense Arena and feature retractable roofs, which can be shut in case of rain or extreme heat. The Australian Open and Wimbledon are the only Slams with indoor play. Held in the middle of the Australian summer, the Australian Open is famous for its notoriously hot days. An extreme-heat policy is put into play when temperatures (and humidity) reach dangerous levels.