Description
Introduction
The term ‘natural cave’ refers to any type of underground cavity not of man-made origin. In most cases, natural caves are formed by processes of corrosion and the chemical dissolution of soluble rocks, such as limestone, dolomite, marble, gypsum, rock salt and calcareous schist, as well as by physical and mechanical erosion processes.
Less common, but still classified as natural caves, are tectonic cavities (cavities formed along fractures or faults and progressively widened by the force of gravity) and lava ‘tubes’.
From a purely speleological point of view, for a cave to be defined as such and to be included in a specific register, it must be accessible to humans and must have a linear length of 5 metres or more; furthermore, the width of the entrance must not exceed its depth.
CAVE REGISTER
The establishment of the register of caves and karst areas in the Province of Trento was provided for by Provincial Law No. 37 of 31 October 1983 (Protection of the mineralogical, palaeontological, palaethnological, speleological and karst heritage); Article 14 of the aforementioned law delegates to the Provincial Executive the power to issue regulations concerning the establishment, operation, updating and access to the register itself
The Trentino Cave Register was officially launched on 14 March 2008 by means of a specific resolution of the Provincial Executive (the regulations approved by the Executive are reproduced in full in the annex).
The earliest reports of any scientific merit concerning the caves of our province can be attributed to distinguished naturalists such as Stenone (b. 1638 – d. 1686; Bus della Giazzera near Ronzo–Chienis) and Antonio Stoppani (b. 1824 – d. 1891; glacial potholes at Nago and Vezzano).
Historically, however, the register was first established in the early years of the last century, primarily by naturalists and geographers – including Cesare Battisti – and hikers affiliated with the SAT’s caving groups (among the most active were the Mattarello and Riva caving groups). From the 1950s to the present day, the register was initially managed by the Tridentine Museum of Natural Sciences and subsequently by the Tridentine Alpine Club; however, in accordance with the aforementioned regulations, direct responsibility now lies with the Autonomous Province of Trento, and in particular with the Geological Service.
For several years now, the Geological Service has been collecting data on the caves within the province in collaboration with the Tridentine Alpine Club, on the basis of an initial agreement covering the three-year period 2005–2007.
The data collected have been verified, supplemented and validated against the geological data and information held in the Geological Service’s archives. All the material was ultimately used to create a computerised database, which also includes the digitisation of paper-based and bibliographic information (surveys, photographs, previous studies).
However, there remains a significant amount of work to be carried out in the coming years, as the management of the cave register requires continuous updating, correction and supplementation of the data, given that these are subject to change following new exploratory discoveries or advances in scientific understanding of the provincial territory.
The work of updating, correcting and supplementing the register’s data will continue to be coordinated by the Geological Service in future, as required by current regulations, with the collaboration of the SAT.
The historical register currently maintained by the Tridentine Alpine Club (SAT) contains over 2,000 caves that have already been catalogued, and it is estimated that a further 300 – 400 of which the exact location is unknown but whose existence is presumed, at least based on information gathered from residents of villages and valleys or on reports from hikers. In total, therefore, there are over 2,300 caves in our province for which we have more or less detailed information.
The official PAT register currently includes 2,265 caves (taking into account the 2026 update).
There are many reasons why it is extremely important to ensure the protection of natural caves.
Firstly, it must be noted that these are unique and irreplaceable environmental assets, which have generally taken several hundred thousand years, if not several million years, to reach their current morphological form.
Caves are also often connected to karst hydrogeological systems of considerable potential and are highly vulnerable to potential sources of pollution. Many settlements in our region derive their water supply from springs connected to karst aquifer systems (for example, in the outlying valleys of the Brenta Group).
Caves also present further important aspects of a scientific, geological, geomorphological, historical–cultural, palaeontological and palaeopathological nature. Indeed, there is no shortage of examples of caves inhabited in prehistoric times (Ernesto’s Cave in Grigno, Riparo Gaban in Martignano di Trento), in historical times (Bus dei Preeri in Avio, Covelo di Rio Malo in Lavarone, Il Colo in Pieve Tesino, etc.). Furthermore, important cave sites containing remains of Ursus spelaeus have been studied. Finally, mention should be made of recent developments in the field of climate reconstruction over the last 500,000 years based on cave deposits (concretions such as stalactites, stalagmites, flowstones, etc.).
Within the Province of Trento, well over 100 caves extend for more than 100 metres, and at least 15 of these exceed 1,000 metres in length.
The longest is the Grotta della Bigonda, whose entrance is situated in the municipality of Ospedaletto; it extends for over 40 km within the northern slope of the Asiago plateau.
Over 50 caves have significant vertical drops, ranging from 50 to 400 metres. These include the Abisso di Lamar (Terlago), the Abisso di Aladino (Daone) and the Abisso di Val del Parol (Brentonico).
Various explorations of the Abisso del Laresot in the Brenta Group have recently been carried out, during which a depth of around 1,000 metres was reached.
No fewer than 133 caves, among the most significant in terms of scientific, historical and cultural importance, have been included in the Provincial Urban Plan as ‘invariants’, i.e. elements that characterise our territory from an environmental perspective. Special protection criteria will apply to these caves, in addition to those already provided for by current legislation for all natural cavities included in the land registry. It is estimated that, with the inclusion in the cadastre of the majority of known caves, the karst cavities listed in the PUP as ‘fixed features’ could reach and exceed 200 in number.
As regards future activities relating to the management of the Register, in addition to data updates, the following have been promoted: geological and stratigraphic studies within the caves; hydrogeological studies to monitor and control underground water flows; the reconstruction of hydrogeological models of the major karst aquifers, and palaeoclimatic reconstructions from cave deposits.