Monte Cucco is first and foremost a park of grottoes. There are hundreds of them, in every shape and size: long and extremely long, deep and very deep. All of them, however, are of great interest to a multitude of disciplines: geology, geomorphology, speleogenetics, hydrology, animal biology, paleontology, paleethnology and history. The formation of the caves, as previously mentioned, took place some hundreds of thousands of years ago by a process of hot liquids, rich in minerals and corrosive acids, rising and flowing through deep fissures in the calcareous rocks.

Every one of the grottoes, at some period, functioned as a source of thermal, sulphurous water. In some cases the temperature of the liquid even reached hundreds of degrees (perhaps even 300° C). This period witnessed the formation of the longest of the galleries, the deepest shafts and the largest chambers, all interconnected in a system many kilometers in length. With the completion of this endogenous (hypogenic) activity, the corrosive, thermal liquids drained away from the cavities, leaving the rain and ground water free to penetrate the surface cracks and enter the newly-created subterranean system. Thus a second phase of speleogenetic activity occurred which, although having little impact on the previously established structure, was responsible for the formation of some very tiny meandering passages and narrow tunnels. The main bulk of the rainfall now flows down into these, later reaching the subterranean water-reservoirs and subsequently emerging through the springs in the valleys. The most significant karstic feature is indisputably the Grotto of Monte Cucco, a vast subterranean system extending for over 30 km and reaching a maximum depth of 923 metres. For a long time it has been recognized as the largest and deepest cavern systems in Italy, as well as one of the most important to have ever been found. At the moment, four entrances to the system are known, all on the eastern flanks of Monte Cucco. The main entrance lies at 1390 m, the Pozzo del Nibbio entrance is to be found at 1509 m (more or less at the top of the mountain), the entrance opening towards Pian delle Macinare is at 1395 m, and now obstructed by a smallish landslip, while the Galleria Nuova access is positioned slightly below the main entrance. The main entrance leads first to a shaft 27m in depth allowing access to a series of enormous chambers in rapid succession.

These are known as the “Cattedrale”, the “Sala Margherita”, the “Giardino di Pietra”, the “Sala del Becco”, the “Sala delle Fontane”, the “Sala Simonetti”, the “Condotte Terminale”, and the “Sala Terminale” (which can also be reached by the entrance facing Pian delle Macinare). This area is the most spectacular part of the system, with some truly incredible and majestic stalactite and stalagmite formations, created by the constant dripping over hundreds of thousands of years of water containing deposits of crystals and limestone particles. A visit to these caverns certainly leaves a lasting impression: it is like entering a vast, dark treasure-house, filled with jewels crafted in rock and minerals. One’s eyes strain to penetrate the shadows and make out the many thousands of sculpted forms covering the immense walls and disappearing into the darkness of the high vaulted ceiling overhead.

Looking down at the floor, amongst the water channels and the limestone stalagmites, one can see lots of tiny emerald pools, where the endless dripping of water creates quivering circles. If the silence seems ominous, the incessant fall of myriad droplets of water gives one a sense of the rainwater draining through the soil and making its way downwards until it reaches the spring known as the Sorgente Scirca. However, the Grotto of Monte Cucco does not come to an end with this series of chambers: indeed, they are only the reception area of the system. There are many galleries and shafts leading off Sala Margherita, giving access to further depths, and chambers of every size. One of these is an uphill passageway known as the Galleria delle Ossa which is one of the most beautiful in the Grotto, pure white and perfectly preserved. It opens into a large chamber whose floor is covered with detritus: the external land surface is nearby and a previous landslide has obstructed yet another entrance. However, the exceptional nature of this place lies in the fact that the whole gallery and final chamber constitute a repository for the bones of ancient animals. Here, have been discovered, on various occasions, the skeletal remains of rhinoceroses, bears, ibex, pine-martens, deer and a type of cattle. All these animals lived at a time when the climate was considerably colder than now: that is to say, during the last Ice Age, approximately 20,000 years ago. There is another passageway leading off the Sala Margherita, known as the Nicchione degli Stemmi, which has only recently been discovered.

This takes one into the actual Grotta di Monte Cucco, the largest and deepest of the grottoes, and the one offering the greatest interest for sports enthusiasts and most salient possibilities for developing scientific hypotheses. It led to speculations about the existence of immense galleries, precipitous drops, ever larger chambers, channels carrying torrents and river, deep lakes, siphons with hidden water-courses, waterfalls, rapids, flooded passages, labyrinths of tunnels and inaccessible underground rivers. It has also become an extremely important and popular location for speleologists, attracting hundreds of enthusiasts, all eager to test themselves in one of the most astounding limestone cave-systems known to man. In addition, it is considered a prime site for research into subterranean hydrology and speleogenesis. Even though exploration is difficult and time-consuming, requiring the navigation of long, dark passages, it offers extraordinary opportunities for observing, first hand, the processes of subterranean water-drainage and natural cave-formation. Monte Cucco and the surrounding Park are also riddled with numerous grottoes, classed as minor systems on the basis of their length and depth, but still of considerable attraction and natural interest.

There is the amazing Voragine Boccanera, a huge, spectacular pothole, reaching to a depth of over 100 m. There is also the Buca di Faggeto Tondo, nearly three kilometers long and 400 m deep, where one can observe the extraordinary crystallization process involving corrosive thermal liquids (chalk, barite, celestine and fluorite). The Grotta Bianca and the Grotta delle Fate are unique of their kind, containing some large formations of bacterial matrix. The Grotta del Menca is lined with a multitude of crystalline limestone formations, produced by the constant dripping of water over the millennia. The Buca della Valcella, twisting and narrow, contains a torrent which eventually emerges as a spring (the Sorgente delle Lecce). The Abisso del Boschetto slices down from the summit of Monte Cucco, gathering water in a subterranean stream which later emerges into the Grande Grotta di Monte Cucco. The Grotta Ferrata is rich in ferrous minerals and cavern fauna, including the rare Speleomantes (cave salamander). The Grotta Nascosta and the Grotte del Drago must have provided shelter in the past for both men and bears. A positive aspect of these minor grottoes is that they are extremely easy and safe to explore. The grottoes of Monte Cucco are associated with a long and complex history of exploration.

The first explorer we know of was Conte Girolamo Gabrielli, who left a written account of his descent into the Grotta di Monte Cucco (possibly as far as the present Sala Margherita) in 1720. However, it was Gian Battista Miliani, the famous speleologist from Fabriano, who carried out the first thorough exploration of the Grotta di Monte Cucco and the Voragine Boccanera during the years 1889-1890. After this, many decades passed until anyone returned to explore the many subterranean passages in the mountain. It was in 1956 that a team from Perugia, Francesco Salvatori, Guido Lemmi, Leonsevero Passeri, Giancarlo Viviani and Franco Giampaoli, began a series of systematic explorations, leading to the discovery and investigation of the whole, vast underground system. This research programme came to an end in 1978. From then until today, continuing research and exploration has been organized by the Centro di Speleologia di Costacciaro (Francesco Salvatori, Emilio Cairoli, Euro Puletti and Andrea Novelli), by the Speleo Club Gubbio (Marco Menichetti, Stefano Tosti and Andrea Pierini) and by the Gruppo Speleologico Valtiberino (Luca Poderini, Pietro Izzo and Sergio Consigli).

They were responsible for the discovery and exploration of all the smaller caves now known to us, as well as undertaking studies into speleogenetic mechanisms and subterranean hydrology. The story still continues, with ongoing discoveries and research programmes.