The cave of San Giovanni with its 850 meters of internal road is classified as the longest carriageable cave in the world, the only case in Italy and one of the 3 cases in the world. It is a suggestive cave where you can admire the karst phenomenon. From a geological point of view, the entire area can be dated back to 530 million years ago, made up of carbonate rocks. Today a destination for many tourists with an attraction of about 100,000 tourists a year, an international choir festival has been held for some years, and above all a destination for speleologists and climbers from all over Europe to climb its walls and secondary branches. In addition to the easy internal road that remained freely open to car traffic until 1999, which represents the main branch, there are also secondary branches whose access is reserved for expert speleologists who include:
• Pireddu's hole (Su stampu de Pireddu)
• Bobore's branch
Adding the main branch to the secondary branches, the cave reaches a development of 3920 meters. Before the construction of the internal road, it is assumed that it was used as a refuge and home as artifacts and pottery dating back to the Neolithic and Byzantine periods were found. In the respective entrances there were prehistoric cyclopean walls (the remains of which are still visible today particularly at the southern entrance), a chapel of Byzantine origin unfortunately demolished at the end of the 19th century to allow the construction of the road. Nonetheless, a commemorative church dedicated to San Giovanni was built in the road to the left of the cave flanking the south entrance. There are numerous historical documents that speak of the cyclopean walls thanks to the numerous travelers of the 19th century. Among the most important are the king Carlo Alberto, the Valery, Francesco d'Austria d'este, the general Alberto la Marmora, father Angius and many others.

The construction of the road, whose material was partially obtained from the walls and the chapel , was started in 1866 by Count Pietro Beltrami and later concluded by the knight Gaetano Semenza to allow the creation of a communication route between the town of Domusnovas and the Oridda valley as it hosted numerous mining activities and they wanted to facilitate downstream transport of minerals.