Geocaching with some fellow DEN LC folks in Silver Spring. It was HOT! We saw three different style of caches; mini(in a film canister), button(small magnetic cylinder, as above) and virtual(contact the owner with answer to questions). These were challenging, and thank goodness Bridget Belardi was there and knew what she was doing! She is quite the expert. I learned a lot and may download the app for my iPhone and try it at home.