At least in North America, there are rules about how much flat ground there is supposed to be past the end of the runway.
But most of the existing airports don’t meet them, and they were all grandfathered in.
In a lot of cases you overshoot you end up in the ocean, but that is better than hitting a bunker that creates nonsurvivable decelerations.
Every airport has beacons and instruments at the end of the runways. But I’ve never seen them be built inside a concrete bunker.
“In a lot of cases you overshoot you end up in the ocean”
That is definitely the case for a bunch of airports on the East and West Coast.
In California I am surprised they did not put in walls to protect the fish.
Lol.