Complex sentence: Just outside of Arles, the first bridge was the officially titled "Pont de Réginelle" but better known by the keeper's name as "Pont de Langlois".
Split into simpler sentences: Just outside of Arles, the first bridge was the "Pont de Réginelle". While the official name of the bridge was "Pont de Réginelle" it was better known by the keeper's name as "Pont de Langlois".