Images Construction techniques in Milan (poles were put under the walls and amphoras under the pavements for drainage) Detail of mosaic floor. III century A.D., found in Milan Detail of mosaic floor. III century A.D., found in Milan Mosaic floor. End III – beginning IV century A.D., found in Milan Screed floor decorated in red. I century B.C., found in Milan

In Roman times, like in medieval times, there were particular building techniques, different from today. Usually cadastral borders remained fixed for buildings throughout the city, so they would build the new constructions over the old ones, without removing the debris. In this context, the mosaics of the new buildings would be laid over the old mosaics. During centuries, the process repeats itself, therefore a vertical section of the floor of Ancient Roman buildings could reveal several strata of mosaics dating from I century B.C. to III or IV century A.D.