It is the Gym Annex in Utsunomiya, Tochigi, Japan. It was built as the indoor training center of Tochigi Prefecture Fire Academy. Now, it is mainly used as a boxing venue.
<a href="//commons.wikimedia.org/wiki/User:Miyuki_Meinaka" title="User:Miyuki Meinaka">Miyuki Meinaka</a>
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>