Pink Tentacle has gathered several galleries of Japanese manhole covers, which vary from cute to terrifying. Manhole covers are fascinating to me; there’s often all sort of encoded information in their designs, like when the sewer was created and by whom.
In New York, my home, large compass decals are being placed on the sidewalks to help tourists—a perfect candidate for new manhole designs. (There’s a nice Flickr pool of NYC manhole covers, too.)
Japanese manhole covers [PinkTentacle.com]
The problem with putting a compass rose on a manhole cover is that workers would have to be very careful in putting the cover back on in the right orientation after using the manhole.
That doesn’t even take into account pranksters deliberately turning the compasses around; all you’d need is a pry bar.
i don’t think the rotating under traffic thing is an issue. it’s either in the street (where pedestrians don’t go, at least long enough to study a manhole) or on the sidewalk (where cars don’t go).
Actually, manhole covers spin around due to traffic driving across them, so they could never be relied upon for directions.
Manhole covers spin around (due to the traffic running over them). So, they could never be used as a reliable compass rose.
My favorite manhole cover is on the sidewalk in Bratislava, and features Cumil the sewer worker peeking out:
http://www.sewerhistory.org/images/mhc/slovak_mhc26.jpg