A few scavenger hunt ideas include "I have roads but no asphalt, rivers but no water" (a map) and "I reverse your view without moving" (a mirror). The best scavenger hunt clues give enough details that the object is discoverable, but it's not so obvious that the hunters guess immediately.
There are several different ways to arrange scavenger hunts so that the hunters have to answer riddles to discover the location of the next clue. There are also photo scavenger hunts, in which each clue is a picture of an object and the searchers have to find the object in the photo. This can be more challenging if the organizer cuts the photo into pieces and makes the hunter assemble them like a puzzle.