The basilica of Saint-Pierre-aux-Nonnains in Metz, France is one of the oldest churches in Europe. The building began life in the 4th century when Metz was an important Gallo-Roman city.
Wikipedia https://en.wikipedia.org/wiki/Basilica_of_Saint-Pierre-aux-Nonnains
Address 3Bis Rue de la Citadelle, Metz 57000, France
Coordinates 49°6'54.248" N 6°10'9.613" E