The lower part, with its majestic, striking environments, gives way to an upper area formed by a tangle of narrow galleries developed on levels located on top of one another. The two parts of the cave are separated by the waterfall of Lake Ernestina. The calcareous concretion made up of stalactites, stalagmites, curtains and icefalls often presents imposing dimensions and exquisitely beautiful shapes and colours.

Explored in 1850 by a group of valley dwellers led by Domenico Mora, it was the first cave in Italy opened to the public on 2 August 1874 by Senator Giovanni Garelli from Mondovì.

Since 1969 it has hosted a scientific station of the Speleological Group of the Maritime Alps of the CAI of Cuneo, focusing on the phenomena, including those of a biological nature, still taking place in the cave. Bossea has 57 species of cave animals, 10 of which are endemic, and the paleontological material revealed by a series of excavations conducted in the space of several decades starting from June 1865 is of great interest. Part of the material was used to rebuild a complete skeleton of the Ursus Spelaeus, now exhibited in the Hall of the Temple.

The constant temperature of 9° C is one of the typical characteristics of all Monregalese caves, something to keep in mind before venturing inside, as it is important to wear suitable clothing and footwear for its cool climate and the dampness inside.