Discovered and partially destroyed in 1869, this amphitheater is Paris's most important Roman ruin after the baths in the Musée de Cluny. Today, the site is home to a small arena, not as grand as the original, and gardens. You may feel as if you've discovered a private spot in the heart of the city, but don't be fooled. Your solitude is sure to be interrupted, if not by groups of students playing soccer, then by parents pushing strollers down the paths. This is an ideal spot for a picnic; bring a bottle of wine and baguettes to enjoy in this vestige of the ancient city of Lutétia.