Grotta dell’Arco di Bellegra

The "La Cona" stream, which emerges from the resurgence, has an average flow rate of approximately 3–5 liters per second.

Systematic investigations of the cave were initiated in 1925 by several members of the Circolo Speleologico Romano, who produced the first morphological descriptions of the site. The rock paintings were discovered only many years later. On 26 January 1999, mr. Roberto Olivieri, a technician involved in the construction of the metal walkway intended for tourist access to the initial section of the cave, identified the group of red-painted figures on the left wall, approximately 40 m from the entrance. A second group of paintings in black color was discovered on 26 October 1999 during geological survey activities. These black-painted figures, located adjacent to the red motifs, were identified by the geologist Claudio Succhiarelli and the topographer Maurizio Schina. Despite the importance of these finds, no formal publication followed at the time.

Grotta dell’Arco: the natural rock arch, with the cave entrance visible in the background (photograph by the Circolo Speleologico Romano, 1932; from Mecchia et al. 2003)

Several years later, Gianni Mecchia of the Speleo Club di Roma brought the paintings to the attention of the archaeologist Tommaso Mattioli, then affiliated with the Department of Human and Territorial Studies at the University of Perugia. This marked the beginning of the first systematic investigation of the paintings, culminating in their formal publication in 2007 and the official recognition of the discovery. Today the cave can still be visited upon request as part of a controlled tourist itinerary

Present-day entrance of the cave with the metal walkway for tourist visits (from sotterraneidiroma.it)

Although the cave had been explored since the 1920s, the question remains as to why the rock paintings were not identified earlier. The difficult conditions of movement within the cavity probably played a major role in this delayed recognition. In the initial sector of the cave, the floor was entirely covered by a thick deposit of soft mud in which visitors could sink up to their knees, making progression particularly arduous. Under such conditions, explorers were forced to focus primarily on their footing, with little opportunity to divert their attention from the ground to carefully observe the cave walls. The presence of these extensive muddy deposits was already documented by the earliest explorers in 1926 and 1932:

Remains of the foundation of the retaining wall of the small dam constructed at the entrance of Grotta dell’Arco (photograph from Succhiarelli 2025).

These muddy deposits accumulated from the cave entrance to approximately 200 m into the interior as a consequence of the silting-up of an artificial underground water reservoir. This reservoir had been created between the 1600 and 1700 through the construction of a dam wall, approximately 3.5 m high, built of stone and cement mortar at the cave entrance. The impounded water was used during the summer months to supply a mill located in the valley below.

Trace left by the muddy deposits beneath the red-painted figures (white arrow) (photograph by Tommaso Mattioli).

Most of the muddy deposits were subsequently removed in 1955 as part of a land-reclamation and drainage intervention. The paintings are located within a small niche and on a vertical wall surface situated approximately 2.5–3 m above the present walking level. However, the traces left by the ancient muddy sediments that once filled the entrance area indicate that these deposits must have reached the lower part of the figures.