The National Park Service is celebrating its 100th birthday this week.
It was created in 1916 with the intention to preserve and care for the more than 400 National Parks across the country that are seen by 275 million people each year.
Arizona's national parks -- Grand Canyon, Petrified Forest, Saguaro -- are each celebrating with cake and activities. Plus, admission to all national parks is free through August 28.
Google partnered with the NPS to help show off some of its hidden gems through its virtual reality series, "Explore The Hidden Worlds of the National Parks."
Using your smartphone or a computer, you can explore Alaska's Kenai Fjords National Park, Hawaii's Volcanoes National Park, New Mexico's Carlsbad Caverns National Park, Utah's Bryce Canyon National Park, and Florida's Dry Tortugas National Park.
In the video below, Google's shows you a snippet of how the project was shot.