Here is an enhanced aerial view of Chofu City Gymnasium 調布市総合体育館 (Chōfu-shi sōgō taiikukan), a grass-covered, subterranean structure that would likely be better known if it weren’t hiding in a relatively obscure section of Tokyo.
Let’s look at the development of the site over the years. It used to be standard farmland as recently as 1974-1978 (below, left). This land underwent a transformation over the next several years, vaguely resembling a golf course during 1979-1983.
In the photos from 1984-1987 we can clearly see the gymnasium under construction. In 1988-1989 the site has long since been completed and looks much like it does today. The building was completed around 1985.
The only change we see between 2004 and 2008 is that a white circle at the bottom-left of the site has been overgrown with trees.
The white circle is a modest pavilion. The change in the aerial photos may be explained by the difference in leaf cover between fall/winter and spring/summer.
And here is the site, as seen from the northwest corner looking southwest:
- Architectural map of Tokyo: