Why are Manhole Covers Round?
Why are man-hole covers round? is supposedly one of the questions that Google used to ask job applicants, and there are lots of answers. Why are some coal hole covers hexagonal? is never asked.
Thehexagonal shape seems to have enclosed a series of honeycomb-like hexagons, perhaps echoing the glass slugs seen on some covers from the pre-electrical era.
Origionally, entry to the coal cellar, now unknown.
This cover was spotted in Tribeca, but its exact location was unrecorded -- yet another layer of mystery.