The Prime Meridian is the universal definition of 0-degrees longitude – but did you know that until recently, there were different prime meridians in use, such as the Greenwich PM and the Paris PM? I only learned this a few minutes ago, when posting this picture I took on the AP-2 highway, near Candasnos Spain between Zaragoza and Barcelona:
You can see the Cypress trees on both side of the arch, which are a well known sight in southern Europe.
It is wonderful that the Spanish would build an arch – but it is a bit sad they didn’t also add a turnoff, so that you could stop and enjoy the moment less fleetingly.