The town of Azay-le-Rideau has more to offer than just one of the Big 6 Châteaux, but you would never know by reading the Michelin Guide to the Loire Châteaux. It's true that the château of Azay-le-Rideau is particularly beautiful, but even a short walk through the centre of the town will provide other architectural gems that I am surprised the Michelin Guide did not feel were worth mentioning.
The church of Saint Symphorien is very close to the château, and if you park in the town's public car park, you have to walk around it to get the château entrance.
The oldest part of the church is 9th century, and it is mostly Romanesque from the 10th to 12th centuries, with additions in the 16th and 17th centuries.
There is a good article about the church here.
front of the church.