I am a fan of Constructs in abandoned places.
But for puzzles you could have something like a decrepit bridge that the PCs have a reason to cross. I might set it up like this:
As you come to the bridge you can see that it is significantly worse for wear. Years of abuse and lack of upkeep have caused the bridge to become fragile and potentially dangerous. There are visible holes in the bridge and the whole thing sags to one side.
(Knowledge Engineering to determine safe squares. Depending on the length of the bridge I would randomly assign the damaged squares. Then if they step on one, allow an appropriate Reflex Save to avoid.)
Or perhaps the whole thing is Illusory and there are a pack of Kobolds/Goblins/what have you camping under the bridge waiting for people to fall through to take their stuff/eat them/what have you.