Morro Bay, on California's Central Coast, is famous for the massive rock formation that guards the mouth of its natural harbor. A remnant of an ancient volcanic plug, Morro Rock--in Spanish, el Moro, the sentinel--was spotted by explorer Juan Cabrillo as early as 1542. Once sacred to Native Americans, it is now a sanctuary for peregrine falcons and other birds, near secluded dunes, a 2,300-acre national estuary known as the back bay, and eucalyptus groves that are visited each winter by monarch butterflies. With the railroad hundreds of miles away, the small fishing town with sandy streets, surrounded by cattle and dairy ranches, once depended on the sea for transportation. Now a thriving commercial district serves both residents and tourists, and its waterfront is packed with busy seafood restaurants. Kayaks, canoes, and commercial fishing boats mingle in the sparkling waters of the bay.