The Rugby World Cup is a rugby union tournament held every four years and contested by the men's national teams of the member unions of World Rugby. The Wales national rugby union team has participated in all nine Rugby World Cup tournaments. Up to and including 2015, hosting of the tournament alternated between traditional rugby heartlands in the southern hemisphere and those in Europe. Wales was the primary host in 1999, with Cardiff's Millennium Stadium built to coincide with the event, and the other three tournaments played in Europe have also used venues in Wales to some degree. Cardiff's Millennium Stadium and its predecessor, the Cardiff Arms Park, will have hosted a total 21 matches over a total of four World Cups. This is the largest number of World Cup games hosted by one venue.