A unique natural tunnel carved by water through the heart of limestone rock for nearly nine hundred meters.
The San Giovanni Cave (Grotta di San Giovanni), located in the territory of Domusnovas within the Iglesiente region, is one of the longest drive-through karst caves in the world. It was once even paved as a road for vehicular traffic and the transport of minerals extracted from nearby mines; today, it is closed to motor vehicles and entirely accessible on foot or by bicycle.
The internal path follows a lit walkway alongside an underground stream. Walking inside reveals stalactites, stalagmites, and massive flowstones blanketing the walls—sculpted over millennia by running water. The soaring height of the ceiling and the width of the tunnel create an evocative atmosphere, where artificial light highlights the natural hues of the rock and the grandeur of the cavernous chambers.
Once you emerge on the other side of the tunnel, you step into the Marganai Valley, a vast forest area crisscrossed with trekking trails and rich in industrial mining heritage. A visit to the cave seamlessly fits into an itinerary that includes the region's decommissioned mining complexes, the town of Domusnovas, and the surrounding limestone crags popular with sport climbers.
