The Grotta dei Santi opens in cavernous limestone on the south-eastern side of the Argentario promontory. The cavity is formed by one vast chamber, 45 m long and 40 m wide (maximum).

It is known that research took place in the cavern in 1869, but it was Aldo Segre who provided a precise stratigraphic description in 1959. From 2008 onwards, the SBA of Tuscany and the University of Siena, in collaboration with the University of Pisa have renewed work on the site.

The main aim of the new exploration was to assess the thickness of the deposit described by Segre. Overall, the present situation generally corresponds with the lithological units he identified.

In 2013, it was decided to proceed with a systematic investigation, given the cavern’s scientific importance and the fact that the prehistoric deposit appears to be eroded by the sea during heavy storms. This erosion risks further damage to the Musterian levels already removed from the part of the cavern closest to the entrance from the ingression of the Holocene sea.

The campaign produced the following results:
1. planning of the cavern;
2. layout of the grid and level 0;
3. new work on the exposed stratigraphy;
4. sondages in the Musterian deposit.
As regards point 3, all of the disturbed soil was removed revealing the in situ stratigraphy. This led to the identification of a series of Musterian horizons with hearths (denominated 110, 111, 1004). Horizon1004 was was quite thick and extended horizontally for at least 12 m2. It was sealed by a clay sediment, and formed by at least three episodes of Neanderthal occupation.

The excavation of sondages in the Musterian deposit was limited to: – the opening of just under one m2 (quadrant H2) in horizon 1004; – the excavation of level 111 in quadrant G5; – the excavation of a sondage (1 × 1 m) below the thick base stalagmite.
The 2013 campaign marked a decisive step in the evaluation of the Grotta dei Santi. In fact, if its importance in the Tuscan prehistoric panorama and more widely that of central Italy) was initially recognised, today it can be said that the Grotta dei Santi is one of the most significant Neanderthal deposits in Europe.