That sentence rates high on being able to make most folk turn and walk away when you mention it but wait! I came across this great blog post on the strange and surprising world of Japanese Manhole Covers. They really are a thing to behold. Each city has one or more unique designs ranging from icons of the city, abstract designs to the plain strange.
It also reminded me I had a couple of photos of the covers from my trip to Japan so had to share.
More here at http://www.kuriositas.com/2012/01/art-of-japanese-manhole.html