These aren't your ordinary rocks! One of the oldest-known religious locations, the Devils Marbles Conservation Reserve is a sacred site to Aboriginal Australians. The site, also called Karlu Karlu, in Australia’s Northern Territory, is home to a collection of giant, gravity-defying boulders. These rocks are composed of granite, and their peculiar shape is the result of millions of years of weathering and erosion.

And what better occasion than Old Rock Day, to appreciate such geological wonders? Did you know that the Earth's oldest rock is truly out of this world? Lunar sample 14321, or 'Big Bertha,' is approximately 4.46 billion years old—just a smidge younger than the Earth itself—and was recovered from the moon during the Apollo 14 mission. Scientists believe that the rock was a meteorite from Earth that hit the moon, only to be brought back home, millions of years later. Whether you're a geology nerd or just a nature lover, today's the day to rock on!