As we traveled by bicycle, we spent a lot of time looking down at the road in front of us, and noticed that every town often had its own manhole design. I soon started taking photos:
In some cases the manholes depicted emblems of the town; in others we were mystified!
Also, I’m not the only one to discover Japanese manholes: https://www.instagram.com/jpn_manhole_collection/ ! And there are even pages for individual prefectures’ manholes: http://asianbeat.com/en/feature/manhole/list_detail.html