Danti's fresco and the new data on the extension of the harbour of Claudius

Antonia Arnoldus-Huyzendveld

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In the Vatican Gallery of Maps there is a fresco of the Portus area, painted in 1582 by Antonio Danti after cartoons of Ignazio Danti. The image below is a copy from the book by Otello Testaguzza: 1970 - "Portus".

It shows the situation of the coastal area towards the end of the XVIth century, as seen from the north in an oblique view. Several details can be recognized, which testify to the reliability of the map. In the upper left the Tiber meander can be seen that was cut off during the flood of 1557 ("Fiume Morto"). Most interesting is the presence on the fresco of several structures in the sea near the coastline. These were also described by several eye witnesses in the XVth century (Flavio Biondo, Pius II Piccolomini, Francesco della Rovere). We know that this was the period in which the coastline advanced very quickly, on average about nine meters per year.

I have digitally stretched, flattened and turned around the original image as well as possible, and have overlain on it the data from the new publication on the drillings and the interpretation of the extension of the harbour of Claudius (2011, Morelli - Marinucci- Arnoldus Huyzendveld). It is surprising to see how well the structures visible in the sea at the end of the XVIth century correspond to what has been found in the drillings.

Legend:
- In red squares the drillings with Roman structures under a cover of several meters of dune sand.
- In red lines the two moles and the lighthouse-island, certain (full) or uncertain (hatched).
- In yellow the drillings with a normal marine sedimentation sequence.
- In blue the drillings with signs of high velocity streams; note that these always occur near structures.
- A green hatched line indicates the probable coastline before the construction of the harbour.