Bue Marino cave is one of the main tourist attractions for those who choose to explore the Gulf of Orosei, and delve into the history and nature of this charming part of Sardinia. Nowadays, it belongs to the second longest karst system of Italy, boasting an uninterrupted network of underground galleries. It stretches for about 72 km from the Supramonte of Urzulei to the crystal clear waters of Cala Gonone. The cave owes its name to the marine mammal that inhabited it until the ‘80s – the monk seal, locally known as “Bue Marino”.

Bue Marino is a complex karst system on its own, subject of regular researches and explorations not only from a speleological perspective but also from a geological and biological viewpoint. It unfolds, indeed, into three different branches, each spanning several kilometres: the Northern Branch, extending for over 10 km; the Middle Branch, consisting of a submerged gallery of about 5 km; and the Southern Branch, currently the only one open to the public, extending for 8 km, and the one that physically connects to the karst system of Codula Ilune. The latter, connecting four entrances/main caves – Su Palu, Monte Longos, Su Molente, Bue Marino – represents the longest underground cavity in Sardinia. One exclusive feature of the Southern Branch of Bue Marino cave is the intersection between the sea and the river at about 1 km deep from the entrance of the cave, which creates landscapes of unique colours.

 

The entire karst system is located within a limestone massif tracing back to the Jurassic period, whilst Bue Marino cave dates back around 4-6 million years. The cavity was excavated by a powerful underground river – the Ilune River – which, swollen by its tributaries, could and still does in certain periods, flood the gallery entirely. Indeed, it is thanks to the strong erosive action of freshwater on limestone that, throughout the millennia, the river has been able to carve such a wide and linear cavity within the mountain, until it found its final outlet to the sea.

 

The numerous and majestic mineral formations along the cave’s path were created by seepage water, mostly rainwater, when the river fluctuated in level within the gallery both before and after finding its way to the sea. This means the cave is still active today, so that it is still possible to see many stalactites with suspended droplets, vast flowstone formations humid, rimstone pools filled with pure and crystalline water, and observe the concentric circles created by the dripping of rainwater.

 

Bue Marino cave represents a significant heritage not only from a geo-naturalistic and biological perspective but also from an archaeological and anthropological viewpoint. Petroglyphs dating back to the Neolithic-Eneolithic period were discovered on the external wall of the cave, depicting scenes presumably associated with worship. Various anthropomorphic praying figures surround two discs, potentially symbolising solar motifs. These petroglyphs are a fundamental evidence that confirm the cultural vibrancy and profound knowledge of the ancient inhabitants about their territory.

 

Accessible by sea from the port of Cala Gonone, the cave maintains a constant temperature inside, ranging between 16°C and 18°C. Visitors will embark on a journey through the first kilometre of the Southern Branch, guided by the emerald waters of the sea and the river, passing through the Room of Chandeliers, named for its concretions hanging from the ceiling, the Room of Mirrors with its spectacular reflections, the Room of the Organ, and finally the Room of the Seal, where the presence of the last Mediterranean monk seal pups was documented in the early ‘80s.