Geocaching is a scavenger hunt where you use a GPS to find a “treasure” at a location. In some cases, you actually get to take something away with you. In other cases, you just take a picture of yourself at the location to prove that you were there (a virtual cache).
The Geocaching web site is the official web site, and you can look up information on caches in certain area. This summer I heard some people talking about locations in Niagara Falls. Apparently there all of the caches in Niagara Falls are virtual as things are too busy to actually leave a little treasure behind. I don’t have a GPS, but the web site shows 2 caches in Niagara Falls that have been found recently: