[ansel12]

Manhole covers are huge and extremely heavy, they don’t bounce around like little water covers and people like plumbers look into manholes fairly often.

Go out and try to remove a manhole cover on your street, it is a challenge.

[Governor Dinwiddie]

You are right. They are damn heavy! You need a strong pry bar at least.

[Does so]

When Formula cars race on city streets, the manhole covers are welded shut. Aerodynamics of the cars create “downforce” which can lift the covers.