Just north of San Francisco, Muir Woods National Monument is home to some of the oldest and tallest redwoods in the world. The area exists solely because of a land donation from an individual back in 1908. At the time, Congressman William Kent was concerned the booming logging industry would forever decimate the old growth forests. Kent bought over six hundred acres of land with a sole view to protecting the redwoods and the mountains above them. The area was declared a national monument by Theodore Roosevelt and named after the naturalist John Muir who's environmental campaigns helped establish the USA's National Park system.
There are three loops ranging in thirty minutes to an hour and half. There are also longer hikes on trails that extend into surrounding Mount Tamalpais State Park. All of these walks offer views of old-growth coast redwoods, the tallest living things in the world.