<human>: Where can I find the best sand dunes in the United States?
<bot>: The best place to find the best sand dunes in the United States is at Great Sand Dunes National Park and Preserve in Colorado. This park offers a variety of sand dunes for visitors to explore, including the tallest sand dune in North America, which stands at an impressive 555 feet high! Other popular sand dunes include those at White Sands National Monument in New Mexico, and at Badlands National Park in South Dakota.