And then there's water. The hard surface you might land on, which is always moving. If you are landing on water, it is certainly not a runway, and has very little chance of being an aerodrome. It's probably hardly a place intended for aircraft operations at all, so lacks the infrastructure, and those things which reassure you, like a windsock, and people around to help, should something go wrong.
And if you look way into the distance like a lot of today's instructors teach you can land right on top of floating objects.