Take a trip to a national park that has some of the tallest sand dunes on the continent. The Great Sand Dunes National Park and Preserve in Colorado is not your average desert climate. It boasts much cooler summer temperatures which are perfect for climbing the dunes. If you are not much of a climber, look at the areas of black sand or enjoy the forests and lakes. The preserve with more than 41,000 acres is worth a visit. If you feel creative, build a sand castle at Medano Creek.