The most useful thing to keep in mind while on your historical quest through Paris is that the Left Bank area surrounding Notre Dame is the oldest part of the city. In fact, within a fifteen minute walk of the ancient church is the old Roman amphitheater, Arènes de Lutèce, the Arènes de Lutèce. It’s hidden up a sidestreet so a landmark worth seeking out. Its ancientness is breathtaking and is a sort of miniature of Rome's gladiator arenas. Lutèce is the ancient name of the city of Paris, when it was under Roman rule.
The Île Saint-Louis, a favorite strolling area among locals and tourists alike, is also ancient. Halfway up the main thoroughfare through the middle of the island is a hotel built around the old tennis courts, called Jeu de Paume, that King Louis XIII erected. The tiny alleyways that are streets in and around Notre Dame and Place St. Michel are historic, too, dating back a thousand years or more, some of them.
Place de la Bastille, with its modern-looking relatively new Opéra House is an historical location where citizens were kept under ball and chain a mere few hundred years ago. Place des Vosges is another one of those monuments that has been so well integrated into the modern urban façade that it’s altogether too easy to forget that it dates back to the era of King Henri II and his Queen, Catherine de Medici (1500’s).