Colorado has 42 state parks that feature places where you can hike, boat, bird watch, picnic, camp, snowshoe, geocache and other activities.
While the state parks sell entrance passes good for one day or one year, you can also get a free pass at 287 libraries across the state.
Each library in the "Check Out Colorado State Parks Program" has two passes to loan out and two "adventure" backpacks. The passes are good for up to seven days. The backpacks have park information and educational activities.