I have spent a lot of time travelling in France. I can think of nothing more romantic than the restored medieval walled town of Carcassonne in the south. When I was there I felt that I was back in the Middle Ages. It's like something out of the days of King Arthur. It looks like something from a fairy tale. Everything is here; turrets, ramparts, dungeons, moats, etc. I think that it dates from the 12th century. However it was restored in the 19th century by the historian Viollet-le-Duc. Many of France's stained glass Gothic cathedrals date from the 12th and 13th centuries; Notre Dame in Paris, Rheims Cathedral, Amiens Cathedral, Rouen Cathedral, Bourges Cathedral, and many others. But I guess the one most famous for its stained glass is Chartes Cathedral (12th C). The facade of Notre Dame in Paris as well as others were restored. The chateaus of the Loire Valley are romantic. Probably the most romantic are Chambord (16th C) and Chenonceau (16th C). There are at least forty more. During the 1800s, medieval styles in architecture were revived. There was gothic revival, romanesque revival and renaissance revival. The 19th century looked back on the Middle Ages as a romantic period. So new churches, palaces and other buildings were produced in these revival styles. I hope that this has been some help to you.
My travels and a lot of reading