Back in the 1960s, construction of an underground parking lot revealed a vast array of archeological ruins under the esplanade in front of Notre-Dame. Specialists were called in and the site was preserved and made accessible to visitors. The ruins are a jumble of centuries of Parisian history, including Roman baths, medieval ramparts, and an ancient port. Explanatory displays have been translated into English, and spiffy 3D displays have been installed to show what Paris looked like during various epochs, which brings many parts of the ruins to life. For some, it’ll still be just a pile of rocks; for others, it’s a fascinating look into the city’s history.