Collegiate Church of Our Lady of Poissy, Poissy

The Collegiate Church of Our Lady of Poissy is a 12th-century church where King Louis IX (Saint Louis) was baptized in 1214, making it one of the most historically significant religious buildings in the Île-de-France region. Founded around 1016 by King Robert the Pious next to the royal castle, the current structure dates primarily from 1130-1160 and represents a rare surviving example of the transition from Romanesque to early Gothic architecture. The church stretches 67 meters in length and features two octagonal bell towers — one stone-spired at 45 meters, the other slate-covered at nearly 48 meters.