Jewel of the flamboyant Gothic, it was built on marshes dried from 1450 to 1623. Remarkable for its Gothic and Renaissance architecture as well as for its stained glass windows (late 15th, 16th and 19th centuries), it also has a swallow’s nest organ (1536) and a 15th century alabaster treasure.Notre-Dame-des-Marais is distinguished by its Renaissance choir (vault-bas-reliefs-balustrade) and its exceptional corpus of stained glass: 35 stained glass windows of the XV-XVI-XIX centuries.