マンホールの蓋: manhoru no futa, means “manhole cover.”
If you travel Japan, you will notice many beautiful and artistic designs on manhole covers. Just about every town and city has its own design. Be sure to take the time and look for them.
Below is the one from my town, Nakagusuku. It has a traditional Ryukuan poem about the town on it, as well as a full moon, a hibiscus, and ocean waves:
とよむ中城 吉の浦のお月 みかけ照りわたて さびやねさみ
The poem describes peacefully viewing the beautiful moon from the castle and the place where Lord Gosamaru held moon-viewing feasts (tsukimi 月見) in the Gusuku era.
Here are a few others: