Muir Woods National Monument

The coastal redwoods here top 250 feet, and standing under them has a way of making whatever you were anxious about feel appropriately small. This 558-acre national monument northwest of San Francisco holds one of the last ancient redwood groves in the Bay Area, with about six miles of trails winding past Cathedral Grove and along Redwood Creek. Serious hikers can push into adjacent Mount Tamalpais State Park when the trees aren't enough.