Rare Rock Arch Formation in Massif de la Chartreuse, France

And it seems it's been only discovered in 2005 (in modern history): "At the end of May 2005 Grenoble climber Pascal Sombardier was exploring the foot of the Grand Manti cliffs situated in the Chartreuse mountains between Grenoble and Chambery. He spied a couloir and decided to explore further... Turning to his right he had trouble believing what he saw: a giant double arch spanning some 32 meters. An expert on the region, he had never heard of this natural wonder."

See beautiful photography of this formation here and read some info here.