One of the fun things that we did earlier in my NCTIES workshop about Google Maps and Earth was to play a couple of rounds of GeoGuessr. GeoGuessr shows you a Google Street View image and a clue to try to guess where in the world the imagery was captured. Playing GeoGuessr is a fun way to get students to look at all of the visual and text clues they have in order to form a good guess as to where in the world they think the imagery came from.
You can create your own GeoGuessr games by using GeoSettr. When you visit GeoSettr you'll see two screens. A map with a Pegman on your left and the Street View imagery for the Pegman's current location on your right. Move the Pegman around, zoom-in if you like, until you find the location that you want people to guess. When you've found the right location click "set round" to save the location. When you've set five rounds (locations) your game is assigned a URL that you can distribute. Just like any other GeoGuessr game when someone plays your GeoSettr game he or she will try to use the visual clues in the Street View imagery to guess the location. After making a guess GeoGuessr shows you the correct location and how far away from the correct location your guess was.
Mission Map Quest, developed by Russel Tarr, is a map-based tool for creating virtual treasure hunts. The concept is simple, you create a series of clues that your students need to follow to identify places around the world. You can add as few or as many clues to your Map Quest as you like. When you're ready to have students try your Quest just give them the web address of the challenge or have them scan the QR code assigned to your Quest.