The Underground

The Underground is a playing field in Super Mario Strikers and Mario Strikers Charged funded by Wario and Waluigi. As its name implies, it is located several stories underground. In the store demo mode of Super Mario Strikers, The Underground was the only unlocked field.

According to the Japanese Super Mario Strikers site, it is located underneath "a certain city", possibly meaning Diamond City. The Capacity is 35,000, it is made out of metal and it is the Star Cup's special field.

Trivia

 * The field's zigzag style in the audience would appear to have been modeled after Wario and Waluigi's mustaches.