The hike to Natural Bridge is an easy and level 3 miles. The trailhead is right by the Bridge Bay Campground. Bridge Creek flows under the bridge and is responsible for carving out the only hole of this kind in Yellowstone. It definitely pales in comparison to bridges and arches in the Moab area, but is still a nice hike and feature to see.
We would have walked right by this quiet marmot if there hadn't been a photographer with his camera pointed at him.