Imagine a vast grassy plain covered with massive herds of elephants, bison and camels stretching as far as the eye can see. Lions, tigers, wolves and later, humans hunt the herds on their huge summer migration. Where is this? This was the Bay Area during the close of the last Ice Age. Take a trip to a time when the San Francisco Bay was just a riverbed, 20,000 to 10,000 years ago.