Because the gym has been shuttered since 2014, when the prefecture deemed its structure unsound, I couldn’t go inside. But where its coffered underbelly tilts up at either end, window walls revealed treadmills gathering dust, a wall clock with hands frozen in place and other traces of a past life. Given that the prefecture intends to raze this modern masterpiece from 1964, time for the so-called Boat Gym may be running out.