Adapted to the shape of the peninsula of Saint-Prex, the historic town has the rare floor plan of an almost equilateral triangle. The main street extends from the gate (in the middle of the north side of the triangle) to the port at the tip of the peninsula. At right angles there are several small cross streets.
The historic city center with residential buildings and partly agricultural outbuildings has retained the character of an agriculturally oriented small town to this day. All that remains of the former fortification is the town gate with a bell and clock tower from the 18th century. To the east of the old town is the castle, of which only the mighty square keep from the original building from the 13th century has been preserved. The current residential buildings of the castle date from the 16th century. The manor house Le Manoir on the southern edge of the old town also has a medieval watchtower from the 13th century. Numerous town houses, patrician houses and farmhouses date from the 16th to the 19th centuries.
Outside the historic town stands the reformed parish church of Saint-Protais, which dates back to the 9th century. The current single-nave building was built in the 12th century (choir) and 13th century (nave). Inside there are wall paintings from the 14th century.
In 1973 the community received the Wakker Prize for maintaining the historically valuable townscape.