Gros Caillou

Gros Caillou (literally "big pebble") is a landmark of the French city of Lyon in the neighborhood Croix-Rousse.

The rock's mineralogical composition suggests it is a glacial erratic, and would have been transported from the nearby Alps by slowly moving glaciers.

Gros Caillou is a metamorphic Triassic quartzite, typical of the alpine regions of Haute-Maurienne and Haute Tarentaise.

[1] The discovery of Gros Caillou dates back to 1861 during drilling of the tunnels of a funicular linking downtown Lyon to the Croix-Rousse plateau.

Had the funicular not been under construction, Gros Caillou would never have been found and relocated to the east side of Croix-Rousse boulevard, where to this day it overlooks the Rhône River and the Alps.