Coyote river flows through 2 active limestone caves building natural bridges near Vallecito, CA, that can be reached by a trail. See the other highlights for directions to find the trail: komoot.de/tour/7889577 There is a Lower Natural Bridge about half a mile downstream from the Upper Natural Bridge, requiring scrambling along the overgrown river rocks but amazing. Ferns hang down over the arched limestone walls to create an exotic landscape. Coyote Creek spills down a smooth-rock channel and disappears in the darkness of the limestone cave tunnels. Water drips down, growing beautiful deposit formations. hikespeak.com/trails/upper-natural-bridge-hike-calaveras-county