Also known as International Dark Sky Park, Chaco Culture National Historical Park, New Mexico, is regarded by night sky watchers as one the best stargazing sites in the USA. Visitors can experience the same night sky that the original residents of the area did a thousand years back. One of the reasons for the exceptional stargazing experience here is that its natural environment has been legally protected by declaring 90% of the area as natural darkness zone, which means that any kind of permanent outdoor lighting is prohibited. This has been done not only to preserve the sanctity of the night sky, but also because natural darkness is essential for the survival of nocturnal wild life as well as for the natural rhythms of human and plant life, which depend primarily on the night sky to remain stable and immutable.