"The Mushroom Rock in the Sahara Desert, Algeria, is a fascinating natural sculpture shaped by the relentless forces of wind and water erosion over centuries. This distinctive geological formation resembles a mushroom, a product of its environment's harsh yet artistically erosive elements."

"A "petrified" ladder in Baume-les-Messieurs, France
The ladder most likely underwent the process of calcification. Being laid on the limestone surroundings known to contain calcium carbonate, when the rainwater poured over, it dissolved the carbonate compounds contained in limestone and subsequently soaked the surface of the ladder in calcium and magnesium ions.
Over time, the minerals solidified on ladder's surface. Researchers estimate the ladder is roughly 150 years old."