From the Proceedings of the Athanasius Kircher Society: Le Mont Solaire.

This past September the French army installed 600 one meter square reflective panels in the shape of Roman numerals on the sands of Mont Saint-Michel, a small rocky island off the coast of Normandy. The island’s 150-foot abbey spire cast a shadow three quarters of a mile long that swept across the numerals, making the timekeeper the largest sundial ever constructed, [continue, see photo]