The ancient capital of the region (Tricastin, named after the original Gallic inhabitants), St Paul sadly has no châteaux - the name is more likely to have been derived from the old name for the city, St Paul en Tricastin. In Latin, tricastri translates as three castles and it seems this also lead to the towns coat of arms which features three towers and a crown.
The village is home to one of France's national monuments, the Cathedral Notre Dame et Saint Paul - a Romanesque structure from the 12th century. It's widely considered to be one of the most complete examples of Provençal Romanesque architecture, characterised by its simplicity, large volumes and perfectly paired building stones. The interior is noted for the carvings on the top floor of the nave.
The town lends itself to exploring, and a nice view can be obtained from the top of the hill. The tourist office offers multilingual audio guides of the main historical sites in St Paul, so you can learn about the Gallo-Roman remains, the medieval town with its Jewish quarter, and buildings from the 17th and 18th centuries. For more detailed information about St Paul's history, visit the Musée d'Archeologie.