Though summer is winding down, it's not too late to pack some gear and head into the great outdoors. There are 113,000 National Parks and similarly protected areas on Earth that you have as your options. Pictured here today is the US and the world's first national park—Yellowstone National Park. With canyons, bubbling hot springs, erupting geysers and bison herds, this UNESCO World Heritage Site, established in 1872, today spans an area of 3,468 square miles. Its many high peaks make a scenic backdrop to meadows, rivers, lakes and forests. Just make sure that you explore them with care and appreciation so that they can be preserved for centuries to come.