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Why are ancient monuments so deep underground?

This post is also available in: Polish (polski)

In 2020, an exceptionally well-preserved Roman mosaic was discovered under a vineyard near the city of Negrar (northern Italy)
In 2020, an exceptionally well-preserved Roman mosaic was discovered under a vineyard near the city of Negrar (northern Italy). You can clearly see the difference in levels. | Photo: Sap Archeologia srl ​​and Comune di Negrar di Valpolicella

Regularly, from time to time, we receive information about the discovery of ancient monuments, including those that date back to Roman times. We can see photos showing mosaics hidden a few meters below the road, pavement or the present ground level. How is this possible?

The main point that should be noted is the fact that there is dust in the air, which is formed from powdered sand, earth and all other elements. The wind regularly blows this material away as part of the erosion process. Interestingly, it happens that sand from North Africa can even be found in Europe.

Throughout history, for example, Rome, the capital of the former Roman Empire and now Italy has been subject to a process of constant reconstruction. The buildings were demolished, the material was used for other structures, and the foundations were either used for further construction or not. The left lower fragments were lost under the piling sand, earth and dust, and then were built up by other objects. Therefore, at present in Rome, at via Urbana, there is the Basilica of St. Pudenziana, under which the walls of Roman houses from the end of the Republic were discovered.

Basilica of St. Pudenzany in Via Urbana. The photo Mr Michał Kubicz shows the difference between the level of the basilica and the modern ground level. It is hard to believe that the difference is actually even greater. The sanctuary is on a level that was actually a tall first floor in the 1st century CE. The former high ground floor is even lower – under the church and the square in front of it.
Michał Kubicz - sekrety Rzymu

It should be mentioned that instead of stone foundations, there are often holes in the posts or slots in the beams, which prove the existence of the building in the past. The wood itself decomposed in most cases and only under conditions of full vacuum could it survive to this day.

It is similar to ancient objects – those abandoned or hidden are found at great depth. For centuries, successive portions of dust are covered with artefacts that, for unsuspecting pedestrians, are deep under their feet. The awareness of how many monuments the earth still hides is beyond comprehension.

The famous square Largo di Torre Argentina located in the center of Rome. There are remains of Roman buildings from the period of the Republic on its territory. You can clearly see the difference in levels compared to modern streets. The square was established at the beginning of the 20th century after the medieval buildings in this area were demolished and Roman monuments were discovered.

Floods also had a large impact on the disappearance of ancient monuments underground. Rising river levels, such as the Tiber, flooded lower Rome, and the applied material was often not removed by returning residents. It got to the point that the ground floors and first floors of tenement houses actually became basements.

In addition, the gradual decline of the Empire of the Western, the transfer of the capital from Rome and winning it twice (410 and 455 CE), resulted in getting the “Eternal City” empty. By the 5th century CE, Rome had only 100,000 inhabitants; the city was only a shadow of the once majestic capital of a mighty Empire, which at the height of its glory had a million inhabitants. After the Gothic wars (535–554 CE), the population dropped to 30,0001.

Abandoned and damaged public buildings were turned into multi-family houses; the famous Via Sacra has been transformed into a pasture for cows; the monuments were covered with dirt. The people who remained in the city used the open spaces and, once full of people, forums for grazing animals or farming. Animals and people applied the new material, and farmers additionally poured better soil so that the plants were better accepted.

Visualization showing the Nerve Forum in the 9th century

Pompeii and Herculaneum – cities underground

A great example of ancient ruins preserved deep underground are Pompeii or Herculaneum – cities that in 79 CE were destroyed and buried by the eruption of Vesuvius. The explosion threw up (estimated at 15-30 km) a huge amount of volcanic material (pumice, ashes), which after some time began to fall. Pompeii was buried with numerous chunks of stone and subsequent dust.

Herculaneum, in turn, did not suffer from the “bombing” with stones. On the second day after the explosion, a pyroclastic avalanche (a mixture of hot gases around 500 degrees Celsius, ashes and rock crumbs) ran down the slope of Vesuvius, which mainly hit Herculaneum. Later, repeated “liquid” avalanches took place, which covered the city with a layer of volcanic mud, even 25 m thick. It was this large amount of material that allowed Herculaneum to remain in a very good condition and hide the city, among others. against thieves.

Excavations in Pompeii at the end of the 19th century.

Many people also ask themselves – why are other ancient treasures still being discovered in Pompeii? How is it possible that in over 270 years, since the discovery of Pompeii, something new is still being found? Pompeii was a wealthy city with numerous public buildings, sports arenas, theatres and temples. The city, with its 64 hectares and nearly 20,000 population, was quite the average social centre of the Roman Empire in the 1st century CE. However, now imagine that one modern city of similar size is buried underground as a result of a single cataclysm. How many everyday objects, buildings, structures and bodies would we be able to find? A lot!

What’s more, so far Pompeii has been discovered only in 2/3 (approx. 44 ha). The remaining part (22 ha) is still waiting to be excavated, but we will not explore some places at all, because modern structures have been created above the buried city, excluding excavations.

Finance is also a problem in the conservation of finds and in conducting further archaeological works. Researchers face this repeatedly, occasionally receiving public support or financial assistance from private sponsors.

Ancient Pompeii areas still waiting to be discovered: regions I-III-IV -V-IX.

Baiae – the city under the water

Another interesting phenomenon is, for example, Baiae – an ancient, fashionable spa with wonderful villas, incl. Caesar and Nero, near what is now Naples. The region is very seismically active, and most of the ancient city ended up as a result of volcanic activity under the waters of the Gulf of Naples.

Roman mosaic located under the water in Baiae.

There have been earthquakes there for millennia. The area is also known for a phenomenon is known as bradisismo – the regular lowering or raising of the ground as a result of filling or emptying of the underground volcanic chambers. It is because of the so-called negative bradisismo of collapsing terrain, much of Baiae is underwater today.

Some of the ruins lie just a few meters deep – here, a tube and a mask are enough to “explore”. Other sunken locations can be seen by scuba diving or taking a boat trip with a specially adapted hull, allowing you to observe the bottom.

  1. Bernard Lancon, Rome in Late Antiquity

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