Just for once don't look up, look down. A manhole cover like the one below is rare, but be prepared to find a great variety of them.
My collection is modest, only 25. I found a few of my favourites in Richmond and Twickenham, England.
Nowadays the real politically correct call them personhole covers (retching sounds, forgive me, my friends).
Yesterday I heard a French woman say plaque d'égout, (but it's not all about sewers).
The Dutch term is putdeksel. The u is pronounced as in cut, not put. Deksel is pronounced like deksel, so that's easy. Don't forget this, it's a good thing to know in case you come to visit.