听力原文：M: Have you ever visited a redwood forest? I recently had a chance to go to Muirwoods National Monument north of San Francisco. W: I've never seen a redwood tree, I really can't imagine how big they are. M: The coastal redwoods are the tallest living things. Some are more than three hundred and fifty feet high. But none of the tree at Muirwoods is that high. You have to go further north in California to see the tallest trees. W: You said that Muirwoods is near San Francisco? I guess it must be quite a tourist attraction. M: Yes. It's less than an hour's drive, so it's easy to go to. W: I've heard that many redwood trees are thousands of years old. Are the ones in Muirwoods that old? M: The oldest documented age for a coastal redwood is more than thousand years. The trees at Muirwoods are 400 to 800 years old. W: Why have they survived so long? M: They have remarkable resistance to forest fires. Their tough, thick bark protects the trees during a fire. The coastal redwoods also like a damp, foggy climate. W: Then since Muirwoods is near foggy San Francisco, it must be ideal for the tree's survival. I can't wait to go there and see them. Where can the tallest trees be found?