Letterboxing is a neat treasure hunt, and can be actively played all over the world. It's a great family activity, as well as good use for teaching and homeschool activities. Re the website:
"Letterboxing is an intriguing pastime combining artistic ability with delightful "treasure-hunts" in beautiful, scenic places. Participants seek out hidden letterboxes by following clues, and then record their discovery in their personal journal with the help of a rubber stamp that's part of the letterbox. In addition, letterboxers have their own personal stamps which they use to stamp into the letterbox's logbook.
And Atlas Quest, dedicated to providing tools and information for letterboxers from around the world, is one of the largest and fastest growing letterboxing sites on the Internet. From stamp carving tutorials to planning a letterboxing road trip, from Aruba to Zimbabwe, you'll find the information you need here."
Type in your city and zip code: You'll probably find lots of letterboxes already close to you!
http://www.atlasquest.com/