In the captivating ‘volcanic’ scenario of the Park of Monte Arci, near the basalt ‘peak’ of sa Punta e’ Santu Marcu, in the territory of Morgongiori, sa grutta ‘e is caombus (cave of the doves) opens up and is a ‘rift’ in the rock - technically a joint - that creeps into the depths of the earth. The crevice, which is 150 metres long and a metre and a half wide, has been known to archaeologists since the middle of the 20th century: the first to cross the entrance and descend the crag, after reaching the bottom of the rift, were amazed: they found a perfectly-preserved basalt stone staircase, squared and one metre wide, consisting of three flights, two visible (with 24 and 22 steps) and the third covered by debris, interrupted by two landings. The steps meander along the crack in “an underground space branching into narrow, winding walkways”, as the ‘father’ of Sardinian archaeology Giovanni Lilliu defined it.