The Basilique Saint-Donatien-et-Saint-Rogatien stands away from the main tourist circuit, but it reaches deep into Nantes history. The church is associated with Donatien and Rogatien, two early Christian martyrs traditionally linked to the city, and the present 19th-century basilica replaced a sequence of older sanctuaries on or near the same sacred ground.
Its twin-towered exterior and large interior make it a worthwhile detour if you have already seen the cathedral and want a broader sense of Nantes's religious geography. The building also carries recent scars and renewal: after a serious fire in 2015, restoration returned the basilica to use, adding another chapter to a site that has been rebuilt more than once.