Wikipedia
M-Wave
is an indoor speed skating oval located in Nagano, Japan. Opened in 1996, the arena has a capacity of 18,000. It hosted the speed skating events of the 1998 Winter Olympics. The M-Wave is equipped with movable stands and an automatically winding artificial lawn machine. The two movable stands, each of which have seating for 1,210 spectators, allow the arena to be converted into various configurations including concert hall or a football field.