Excavations have revealed traces of buildings and monuments spanning the 3C-19C beneath the parvis of Notre Dame cathedral. These include two Gallo-Roman rooms heated by hypocaust, the foundations of the city walls from the late Roman Empire, the cellars of houses along the former rue Neuve Notre Dame (some of which can be traced back to the Middle Ages), the foundations of the Hospice des Enfants Trouvés orphanage built by Boffrand, and part of the foundations of Sainte Geneviève des Ardents.