Glassblowing artist Josh Simpson creates imaginary planets that have landmasses, oceans, mountain ranges, volcanoes, even clouds. His big mega-planets, shown at a variety of museums, are 30 centimeters in diameter and weigh 23 kilograms. But he also makes small orbs a couple of centimeters across, which are being placed surreptitiously around our own Earth.

Simpson’s inspiration for his clandestine Infinity Project came from some marbles he found a long time ago on his property in Shelburne, Mass., which appeared to have been lying there for decades and yet were still as brilliant as ever, thanks to the long-lasting properties of glass. Today, more than 1,700 people have hidden his small planets in all sorts of locations—from the gravesite of John Belushi to a castle in Lithuania to an abandoned British fort in Bundi, India—and Simpson still provides them to applicants who present a novel plan.

Each globe is marked with an infinity symbol. Some are meant to be discovered quickly, others are likely to remain hidden for centuries. “I hope future archaeologists will be confused about the meaning and purpose of the little spheres, wondering what they are and how they got there,” Simpson says with a smile.

>>View a slide show of people leaving Simpson’s little planets in spots around the world.

The slide show here identifies people who have placed planets, and the locations they chose. All photos have been submitted by the volunteers and were taken by them or anonymous friends. Related photos showing Simpson’s work can be seen here.