Salerno, like many ancient cities, is literally built upon itself, layer upon layer, in a slow accumulation of centuries. 

• Natural deposits: floods, landslides, and river sediments from the surrounding hills have gradually raised the ground. Rubble from demolitions: each era has destroyed and rebuilt, leaving behind layers of ruins. 

• Architectural reuse: columns, marbles, and Roman floors were incorporated into medieval and Baroque structures. 

• Urban expansion: new roads were elevated for practical reasons—including improving drainage or stabilizing pathways. 

In the Salerno archaeological sites (such as in the historic center), it is not uncommon to find mosaics, opus sectile floors, or remains of Roman domus several meters below the current level. It is as if Salerno has left behind deep but hidden testimonies. This stratification makes the city a sort of living palimpsest: every step we take in the present literally treads on the past.

Salerno is one of the Italian capitals that has the largest number of watercourses on its territory: about twenty-five, almost all of modest size, but many of which are of a regular nature, testifying to the abundance of waters that radiate from the hills to the sea, for the whole width of the hilly belt that forms the background of the consolidated city. The physical landscape, the economic settlements, the social activity and the natural hazards characterizing this area depend particularly on water: meteoric, riverine and marine. 

During the Roman times, the city of Salerno was delimited by two small rivers named the Rafastia (Nord-West) and the Fusandola (Nord-East). Few traces of this period are now visible because many buildings were built during the Middle Ages, often on areas buried by the debris of the floods of these rivers which periodically affected the city, such as that of the IV-V century AD.

The presence of spring emergencies, such as those of Plaium Montis, and the streams - the Fusandola to the N, the S. Eremita and the Rafastia to the S - were certainly determining factors for the fortune of Salerno in the Middle Ages, favoring the development of a real system of gardens with terraced cisterns, of private and public thermal baths and contributing to the supply of fresh water in the port area.

In about 240 AD Gordiano III, after a disastrous flood that had caused extensive damage and had damaged the road that connected Salerno to Nocera, ordered restoration work.

After that, in the current Piazza Abate Conforti was found the base of a statue erected by decree of the "ordo populusque salernitanus" in honor of the patronus Annius Mecius Graccus for having contributed to the reconstruction of the city damaged by the floods and for having built an underground drainage channel from the Castle along the Via dei Canali to Porta di Mare.

The structures in opus reticulatum on which the palatine chapel of Arechi (San Pietro in Corte) was raised belonged to the frigidarium of large public baths already abandoned before the debris of a flood invaded them, at the end of the 4th century or in the first years of the 5th.

A landing point was installed at the Fusandola estuary, when the port at the mouth of the river was abandoned, perhaps in the 1st century AD, at judging from the discharge of Dressel amphorae 2 - 4. The nearby public baths of San Pietro a Corte are, in fact, datable between the end of the 1st and 2nd centuries AD.

The planting of the cemetery on the harbor baths does not indicate only an impoverishment of the city, but it could also mark the abandonment of the landing place, deactivated within the first half of V century probably due to the flood attested by the inscription of Annius Mecius Graccus.

Traces of this flood are also found in the archaeological levels identified in via Giudaica, where an alluvial deposit was found to be related to the abandonment of a landing point near the Fusandola estuary. The material found in the upper layers can be dated between 5th and 6th century AD, when the beach was equipped with one dock for small boats. 

In general, if it is possible to document, after the catastrophic events of the 4th-5th century AD, a resilience thanks also to the intervention of rich possessores, during the 6th-7th century the situation is slowly changing.

The extension from about the middle of the 7th century AD of burial grounds on previously built areas could be the a sign of a process not of depopulation but of further deconstruction within new urban reorganizations.

A thunderstorm is also linked at the legendary foundation of the Schola Medica Salernitana; it is reported that a Greek pilgrim named Pontus had stopped in the city of Salerno and found shelter for the night under the arches of the Arcino aqueduct. There was a thunderstorm and another Italian runner, named Salernus, wandered in the same place. He was hurt and the Greek, at first suspicious, approached to look closely at the dressings that the Latin practiced to his wound. Meanwhile, two other travelers, the Jew Helinus and the Arab Abdela had come. They also showed interest in the wound and at the end it was discovered that all four were dealing with medicine. They then decided to create a partnership and to give birth to a school where their knowledge could be collected and disseminated.