Moving back as far as the Roman times, in ancient Rome Man has started using stone to cover drain covers.

The layman term for drain cover (grate) is manhole cover. Say "manhole cover" and images of spies/heros making use of the underground sewage system popping out of manhole cover in Hollywood films appear.
Historically ever since Man invented the sewage system since the Roman Times to drain water and urban waste away for sanitation purposes, manhole covers (drain covers or grates as we would prefer to call them) have already been invented out of the basic need in order to avoid people from falling into underground sewage and also prevent large objects from entering the drains which cause choking which eventually can cause flooding.
Fast forward to the modern day, the sewage system is still utilised under all cities around the world. As opposed to 6 inch drain cover covers the Romans use in the ancient days, we now have special steel reinforced stone gratings that provide the thousand year old function of covering the inlets of our sewage system.
A lot more than a cover, check out Jonite's range of drain covers (drain gratings) here: https://www.jonite.us/products/creative-grates