Oregon Caves National Monument - http://www.nps.gov/orca

Oregon Caves National Monument is small in size, 480 acres, but rich in diversity. Above ground, the monument encompasses a remnant old-growth coniferous forest including a Douglas-fir tree with the widest known girth in Oregon. Three hiking trails access this forest. Below ground is a marble cave created by natural forces over hundreds of thousands of years in one of the world's most diverse geologic realms.