It is a combination of natural and partly artificial caves connected both to the overhanging Monastery and, underneath, with a thick web of tunnels which were once caves of the Roman aqueducts once. This place has always been considered as a destination of spiritual concentration and meditation. The first human settlements in this area date back to a more ancient time; in fact, in the early 20th century the remains of a burial dating back to about 8,000/10,000 years ago were found during the construction of the dam. As early as May 1865 in the "Grotta della Sirena" (near the river Licenza) two tombs with their own grave goods dating from the Lower Paleolithic came to light. This rupestrian complex owes its fame to the stay of the Saint coming from Nursia in 503 A.D. A small community of Anchorite monks lived in this area. Once having lost their abbot, this community had the honour to welcome Saint Benedict as their new superior. The Saint unwillingly agreed to this role because he was convinced that his way of life could hardly embrace the habits of the local monks. Indeed, his rigid observance of the rules soon gave birth to the discontent of the brothers who attempted to poison him during a dinner by putting poison in his wine glass. Saint Benedict broke the glass with a sign of benediction and, in so doing, he escaped from certain death; in the face of such an extreme gesture, he understood that his stay was useless and left the community. The attempted poisoning occurred inside the cave which is now called "Saint Michael's ancient oratory". The caves' complex can be accessed through a small door facing the entrance of the church and is now open to the public again thanks to its recent restoration. By going down the stairs excavated in the rock, you can admire the distinctiveness and the beauty of this rock caves shaped by the karst action which contributed to the creation of an unusual and evocative set of caves and inlets. At the end of the staircase, on the left, you can see a small cave - once used as ossuary and later walled-up - and a bigger cave, transformed into a rocky chapel and dedicated to Saint Michael the Archangel. The entrance is characterized by the presence of a molded stone portal of the 15th century coming from the church above and hereafter readapted. When entering the cave, you can observe a room excavated in the rock with an apsidal niche and two large frescos on the lateral sides: on the right, there is the representation of the attempted poisoning of Saint Benedict; on the left, Saint Francis attempting to convert the Sultan; whereas at the centre of the apsidal niche there is a Regina Angelorum on the throne between the Archangels Raphael and Gabriel. In the niche behind the altar, there is the Glory of the First and the Second Franciscan Order where you can recognize the Blessed Filippa Mareri, St. Clare of Assisi, St. Francis of Assisi, St. Peter of Alcantara, St. Anthony of Padua, St. Bernardino of Siena, and St. Louis of Toulouse. The apsidiole is framed by floral decorations and symbols praising the Virgin; above the altar - among fake marble frames - there are three paintings: The Transfiguration at the centre; Saint Francis grafting roses in the Sacred Cave garden in Subiaco, on the left; and Saint Francis again receiving the stigmata, on the right. All the paintings and the decorations were painted by Antonio Rosati and date back to the end of the 7th century. Actually, the rock complex is characterized by a second group of caves - no longer connected to this first area - where there are the cells which housed the hermits. This second group of caves ends with the chapel dedicated to St. Benedict, considered his personal cell during his stay in San Cosimato. A second entrance in the garden - located at the backside of the convent - gives access to this group of caves, but the negligence and the action of time do not allow its usability. The room of the chapel of St. Benedict - supported by a natural pillar - is partly excavated in the rock and partly closed by a masonry. There are two altars inside it: a smaller one with a small half-moon niche, the other one - realized by Rosati in 1683 - having a small square aedicule with the representation of St. Francis and St. Benedict standing in adoration within it. In the masonry part of the chapel, a big window give the believers who could not access the seclusion a chance to see the altar from the street, benefiting from an indulgence.