In response to this I've come up with a few ideas. For the pool, have the PC's look into it to find the reflection one of their inner self. For instance, a thief who is forced to be an outlaw might see an honest man staring back at him. At the abandoned campsite, the PC's can find evidence of a struggle. For instance, blood marks, items broken, a bloody dagger etc. At the stonehenge type- place, there could be ancient runes which gives a riddle. A quest can be made from discovering the answer to the riddle.