The Baptistery of St John in Poitiers is claimed to be the oldest existing Christian building in France. Built in about 360 but much altered, it is worth half an hour (at least) of anybody's time.
For a plan of the building, there is a good link here, and for more information check out Wikipedia
Live Action Heritage Conservation - Heritage conservation work is going on all the time in the Touraine Loire Valley chateaux. These days the best practice approach is to ensure the visitors ...