One of the global sites containing ancient stone spheres is located in France, in the village of Saint-André-de-Rosans (Hautes-Alpes department).
Some spheres can be found in the village center, visible in gardens and public spaces. Many others are scattered along road D425, heading toward the Col de Palluel.
The most significant site is Serre d’Autruy, a hill accessible via a trail that leads to a sandstone plateau rich in these formations.
Appearance and Characteristics
The spheres range from 60 cm (24 in) to nearly 2 meters (6.5 ft) in diameter and have a rounded shape—sometimes oval, sometimes perfectly spherical.
What makes these spheres unique is that they are embedded in compact sandstone layers, which is why an artificial origin is almost entirely ruled out.
Inside, they show concentric layers and have a composition very similar to the surrounding sandstone—often harder and darker in color.
Most Widely Accepted Theory: Geological Origin
They are believed to date back over 100 million years, when the area was part of an underwater slope known as the Vocontian Trough. Being embedded in the surrounding sandstone, this is considered the most plausible explanation. The sand that formed the massive sandstone beds containing the spheres was deposited by underwater landslides during that time.