You'll find square hole covers all over, they're not rare at all. The strength of the lid and its ability to be supported is not at all an issue on a single human sized hole - it's a thick, relatively cheap slab of metal over a small opening. They're the strongest surface of most roads, by a HUGE margin.
You'll find square hole covers all over, they're not rare at all. The strength of the lid and its ability to be supported is not at all an issue on a single human sized hole - it's a thick, relatively cheap slab of metal over a small opening. They're the strongest surface of most roads, by a HUGE margin.