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 classical 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」
In Okinawan the pronunciation would be: トゥユムナカグスィク ユシヌウラヌウツィキ ミカギティリワタティ サビヤネサミ, fairly from the different than standard Japanese reading.
The poem describes peacefully viewing the beautiful and peaceful moon from the castle towards (what is now) Yoshinoura Park, and there seems to be no worries about accidents or sorrow; this area was the place where Lord Gosamaru held moon-viewing feasts (tsukimi 月見) during the Gusuku era.
Here are a few others: