Paris is young by European standards. Much of the city dates from the 19th century and there are large areas developed more recently than that. But Napoleon III's plan for urban renewal left plenty standing for the 21st century history buff -- the medieval Louvre, the 17th century Place des Vosges built by Henri IV, the vestiges of a Roman amphitheater, and remnants of the city's walls erected by Philippe-Auguste as he headed off for the third Crusade at the end of the 12th century, just to name a few.
But what's particularly intriguing to me is seeing how these periods layer on top of each other. Sometimes it's quite physical as in the photos below, of the Hôtel de de Sens, one of just three medieval buildings erected as private residences that are still standing in Paris. Located in the Marais, between rue Saint-Antoine and the Seine, it dates from the earliest years of the 16th century and was the Parisian residence of a provincial archbishop.
Now look again below in this closeup of the area circled in red up top, you'll see a black dot and the date: 28 juillet (July) 1830. That's not just any black dot...it's a cannonball, shot during one of several revolutions of the 19th century, and immortalized forever.
There are countless other examples of the physical layering. Just go down into the archealogical crypt in front of Notre Dame, for example, and you can see the basements and roads of Roman, medieval, and later eras piled atop one another. And sometimes the layering is just the sense of history that hangs on your shoulders as you walk the streets -- plaques commemorating fallen victims of the Resistance, carved notices citing a 1881 law not to post notices on public buildings, church facades desecrated by revolutionaries, cobblestones peeking out from under asphalt. It's not hidden away in a museum; it's just a part of life, present connected to the past.
American history? Practically current events. French history? Current events informed by a deep sense of happenings, ideas, and forces several thousand years in the making.