From the Super Mario Wiki
Grand Stadium is the last of the four stadiums in the soccer mode of Mario Sports Superstars, as well as being the only locked stadium from the start. In order to unlock it for use in Exhibition matches, players must clear the Star Cup. The stadium lacks a day and night feature, unlike other stadiums, and just as the baseball mode's Harbor Park, although the course icon shows the stadium taking place at sunset, during and after the match, the match is played entirely at night. This stadium is used for Champion's Cup finals.