The Lateran area is a privileged place for the study of the ancient topography of Rome. Several excavations give us a relatively accurate idea of ??the Caelian Hill, although many of them are only partially published. We also have valuable references to the Caelian in the written sources, which need to be interpreted from both a philological and a historical and topographical point of view. This chapter offers an overview of the evidence, proposing revisions and corrections of some relevant issues at the center of discussion in recent years. It also explores the issue of private houses and the first seat of the Bishop of Rome in connection with the Lateran Basilica. The aim is to outline in a more precise way the urban evolution of the Lateran, which is particularly important in the transition from mid-imperial Rome to the late antique and early medieval city.