M-Wave — officially the Nagano Olympic Memorial Arena — is the speed skating oval built for the 1998 Winter Olympics, located in the Nagano Sports Park on the eastern side of the city. The roof's sweeping wave profile makes it one of the more architecturally interesting structures in the region. The arena is open to the public for recreational ice skating during winter months, and the 400-metre oval gives a striking sense of scale when you step out onto ice that once hosted Olympic competition.
The surrounding Nagano Sports Park also contains the Big Hat ice hockey arena, the Aqua Wing aquatics centre, and an athletics stadium — all Olympic legacy venues from 1998. The complex is about a 20-minute bus ride from Nagano Station. For visitors with an interest in modern sports infrastructure, or who simply want to skate on an Olympic oval, it is worth the journey out. The venues are well-maintained and actively used; calling ahead to confirm skating sessions is advisable.