> Cansiglio sinkholes and abysses <
A symbol of the Serenissima Forest’s karst landscape
Abyss n.
from the Greek a- meaning “without” and byssós meaning “bottom”
A natural cavity, usually very deep, characterized by a predominantly vertical development.
Cansiglio sinkholes and abysses
- 49 recorded caves
- 5,8 km of loop trail
- −794 m the deepest abyss
In the Friuli Venezia Giulia Regional Register of Geosites and Geoparks (CaRGeo), the area between the Bus de la Lum and the Candaglia road, which falls within the municipalities of Polcenigo and Caneva between 1,030 m and 1,200 m above sea level, is recognised as the “Cansiglio Sinkholes and Abysses” Geosite of National Interest. This area is of considerable geomorphological and hydrogeological importance, and representative of the Cansiglio – Cavallo Massif. It is characterised by a concentration of Karst depressions, called sinkholes (or dolines), and abysses. The latter are deep, vertical cavities with open-air access shafts. Among the best known are the Bus de la Lum (15/153FR, 186 m deep) and the Abisso del Col della Rizza (904/410FR), at 794 m the deepest cave in Western Friuli. Influenced by faults, these shafts have a predominantly vertical development, with similar morphologies while some sections have important numbers of concretions that are amongst the most beautiful on the entire mountain. The surface landscape consists primarily of Karst blocks and funnel- or bowl-shaped sinkholes, often aligned along fractures. They result from the chemical dissolution of Cretaceous limestones containing rudists. These were molluscs with cone-shaped shells. In the Veneto region of Cansiglio, the external morphology is less rugged because the “Scaglia”, a marly rock with flint that covers the underlying limestone and erodes more slowly, is still present.
Cansiglio contains around a hundred caves that drain its waters into the area of Polcenigo and Caneva. Tracer tests conducted in 2008 and 2016 by the Universities of Ferrara and Bologna focused on the Col della Rizza Abyss and demonstrated the hydrological connection between this geological site and the Santissima and Molinetto springs, which, together with the Gorgazzo, emerge in Polcenigo and Caneva to form the Livenza River.
Rainwater from the mountain takes just over a week to reach the area at the foot of the mountain along various very long and tortuous routes below ground.
Interactive geosite map
The path of theRing of the Abysses and the 49 caves recorded by the regional speleological cadastre. Tap a cave to open its sheet.
Elevation profile of the loop
The “Doline e abissi” trail
The “ e abissi del Cansiglio” geological trail was created with the aim of raising awareness and promoting this geological site of national importance, passing close to the most important caves. Its circular route winds along trails and forest roads. 5.5 km long, it has an elevation gain of approximately 250 m. It begins at the Bus de la Lum picnic area in the Pian Cansiglio and follows the short trail that enters the forest directly from there, either counterclockwise or clockwise, following the Slipari trail and then the “O” trail that passes close to the Abisso del Col della Rizza. The latter can also be reached from Crosetta along the Candaglia gravel track after approximately 3.5 km. The trail is suitable for everyone, but requires caution as the Karst environment features rocky crevasses, potholes, and funnel-shaped sinkholes. It is essential to stay on the marked trails, as some of the caves are not fenced. Caution and appropriate behaviour during the hike are essential.
- 5,8 km loop
- 964–1171 m above sea level
- Start Bus de la Lum car park
Understanding karst
Video insights on block karst, rudists and corals, and four immersive 360° videos inside the abysses. Each cave’s mini documentary is on its own sheet.
How deep the abysses go
The 15 main caves of the geosite, from entrance to bottom. The Abisso del Col della Rizza, at −794 m, is the deepest cave in western Friuli.
Cave sheets
Data from the regional speleological cadastre, combined with texts and materials from the guide.
FVG Regional Speleological Cadastre (Autonomous Region of Friuli Venezia Giulia, IODL 2.0 licence), data as of 31/10/2026; geosite area approximate (own elaboration).
Explore
Sheet, audio guide and immersive environment for each place.