Imagine my surprise as I was furiously pedaling west toward Saumur on Route des Ducs d'Anjou (hey I didn't name it I just rode it) when I stumbled upon this sign. It marks the prime meridian. That's 0° longitude! It's the reference from which all other lines of longitude on the globe are derived. It is also the line that - longitudinally speaking - divides east from west. I only wish I had my GPS with me so I could really geek-out and see all the zeros.