Set aside a half day the next time you're in Joshua Tree National Park and hike the Wall Street Mill trail. The round-trip distance is less than two miles, but there is a lot of history and desert gold along the way. It's an easy hike, but could end up taking you the entire day if you like to roam and explore as much as I do. I generally make sure I have plenty of water and some trail munchies, and then I don't worry about the time. I just go and wander and generally find something I haven't seen before.