Andy Goldsworthy plots the curves of new Presidio creation

A newly built trail and boardwalk on the southern edge of the Presidio is as much a window into San Francisco's maritime history as it is a path through restored sand dunes and coastal habitat.

May 2011 marks the 10th anniversary of the $34 million restoration of Crissy Field, a 1.3-mile stretch of shoreline between the new Crissy Field Center on the east and the Warming Hut on the west - one of the great vistas anywhere.

The flower beds that once served as colorful buffers for the notorious former prison site known as the Rock have been restored thanks to the efforts of the Alcatraz Historic Gardens Project.

Spotted owls are one of the most iconic threatened species in the West. But despite two decades of work to bring them back, their numbers are still declining. That may be due in part to a new threat - not from humans, but from other owls.