The goes up again of the thermo waters in surface it was not continuous by the time, but no very often it was disturbed by alluvial floods due to the course of water that, limiting the ability of gone up again of the water, it provoked a temporary stasis of sedimentation. At the end of the flood, the thermo water regained their ability of gone up again a new cycle of sedimentation it was established. That’s why the reason that the travertine has in benches or layers sometimes delimited by a light clayey level, due surely to the flood of the time. The whole of all these cycles of sedimentation has filled the ancient area depressed of the basin of Tivoli and Guidonia, Rome, assuming the current rather flat forme.