If your trip to Treguier is all locked in but your travel itinerary is a bit on the empty side, we can give you a few hints and tips.Stop by Cathedrale Saint-Tugdual de Treguier. It's one sight you'll usually find on many travelers' must-do lists. If you still have room on that travel schedule, Jardin du Kestellic and Maison d'Ernest Renan will keep you busy as well.