The "real" San Francisco lies below the streets, sidewalks, and buildings, hidden from view. This famous city is known for its beautiful setting of water, trees, hills, and beaches, but relatively few people know of its true natural state. Before it was built up and paved over, the earth here was a diverse ecosystem of creeks, marshes, sand dunes, estuaries, and densely forested hills. Over this landscape roamed elk, rabbit, bears, bobcat, and mountain lion, and the now-crowded bayfront teemed with mollusks, otters, dolphins, and whales, while huge flocks of birds blocked out the sun overhead. Today, only about two percent of the city's natural areas remain as they were.