Reims is one of the most important cities in French history, and if you are only slightly interested in this subject (maybe slightly confusing but very interesting), then this city is a must. It was the site of over 30 coronations of kings of France, beginning with Frankish leader Clovis (Chlodwig) being christened by bishop Remigius (Rémy) in the 5th century, becoming the first Christian king of France. The cathedral is a real masterpiece of Gothic art from the 13th century, and the former palace of the archbishops, the Palace of Tau, merits a visit as well. The basilica of St-Rémy contains Rémy's tomb and a collection of fascinating 12th-century stained glass windows. There's also a cryptoporticus, showing remains of the Roman Forum. All in all, a fascinating place to visit and very important historically, architecturally, culturally, and religiously.