To find San Francisco at its most natural, head to the source of Islais Creek. You can find it — a trickle of a stream in deeply wooded wildland, 60 acres of what the city's eastern side was like before people. One of the Bay Area's last remaining freshwater creeks sustains wild berries, native chaparral, coyote brush, and wildflowers, while at the end of one of the narrow trails is a hidden rope swing. Towering natural rock formations on either side make Glen Canyon the city's wildest public park and the finest spot for enjoying nature, such as red-tailed hawks and great-horned owls, without leaving everyday urbanity too far behind.