We here observe several places in Rome that offer dramatic evidence of how much ground level has changed over Rome's long history. Doing so deepens our understanding of how much time has passed since antiquity, of how transient some human achievements are, of how depopulated Rome became during the Middle Ages, and of how much we need to use our mind's eye if we are to going to see Ancient Rome well. The effect is especially noticeable at lower elevations and near the Tiber, whose flooding was an important contributor to the rising level of debris that filled the city. The Pantheon, Piazza Navona, the Roman and Imperial Forums, and San Clemente offer clear evidence of these changes. Markers on the sides of buildings indicate the levels reached by the Tiber during memorable floods. My main goal is to help you imagine a once-great imperial capital becoming so neglected that it fills up with mud.