Atlas Obscura on Slate is a blog about the world’s hidden wonders. Like us on Facebook and Tumblr, or follow us on Twitter.

Thinking about grains of sand as stars in the sky is a common way of trying to visualize the enormity of the universe. But at a few beaches in Japan's Okinawa prefecture, the sand grains really are stars.

Take a stroll along Hoshizuna no Hama (Star Sand Beach), located on Iriomote Island, and your feet will become encrusted with tiny star-shaped "tests," or shells, produced by microscopic, unicellular protists known as Foraminifera. When Foraminifera die, their shells remain in the sea and the tide brings them ashore. In the case of Hatoma, Iriomote and Taketomi islands in Okinawa, this results in beaches sprinkled with star sand.

The Foraminifera phylum includes some 10,000 species that create shells of various designs. Star-shaped shells, such as the kind above created by the Baculogypsina sphaerulata species, are rare.

Visit Atlas Obscura for more on the star-shaped sand of Okinawa.

Other intriguing beaches around the world:

• Bowling Ball Beach is filled with mysterious round rocks
• This black shoreline is made up of exploded lava particles
• Dead Horse Bay is scavenger heaven for vintage glass enthusiasts