A scholarly examination reconstructs the ancient topography and hydrology of a cluster of small lakes north of Milan, describing their shapes, relative positions, outlets and interconnections. It assesses classical testimony, especially a passage by Pliny, and surveys antiquarian and local traditions that the basins once formed a single larger lake or were altered by seismic or fluvial events. The narrative compares maps and earlier writers, records notable local observations such as subterranean lignite, and argues for further geological and topographical investigation to clarify how the modern lakes originated and related to ancient descriptions.