The area around the fault called La Falla del Moraig constitutes a unique geomorphological element and is listed as a Site of Geological Interest by the Geological and Mining Institute of Spain (Instituto Geológico y Minero de España). There is a particularly prominent rock wall overhanging which comes out from the ground, where one can clearly see the fault plane and the vertical striations caused by the friction of the calcareous materials during its formation. The Falla del Moraig, also called Riu Blanc, is a fracture of the Earth’s crust (with vertical displacement) that occurred 11 million years ago, during the Late Miocene. This fault deepened the calcareous materials and formed the cave called Cova dels Arcs.

Cova dels Arcs is located at the entrance of Cala del Moraig. Sculpted by the sea, it is one of the best examples of drainage of a karst system that has gone from continental or coastal environmental conditions to submarine. The cavity was initially created under subaerial and flooded conditions during the last rise in sea level (about 60,000 years ago).

Near Cova dels Arcs, a few metres to the south, the entrance to the Moraig underground river can be found, where the Benissa aquifer discharges. It is a wide gallery from which a main duct departs. Deep down, it ramifies, creating bifurcations and galleries. The explorations carried out by underwater speleologists have made it possible to discover two kilometres of completely submerged conduits, which reach a depth of 60 metres below sea level. Its outlet lagoon is located next to the vertical wall of La Falla del Moraig. This system, formed by various galleries, wells and bifurcations, constitutes, together with that of the Greek island of Kephalina, a unique hydrogeological phenomenon worldwide and it remains to be discovered whether it is the deepest underwater river in Europe.

Riu Blanc or Riu del Moraig is only accessible to speleological divers with knowledge and specialised equipment, as it is extremely dangerous because it only has one route and one exit to the surface, so there is a risk of getting stuck in it. A few metres from the fault, there is a magnificent example of a collapsed sinkhole or doline, known as Vasenilla. It constitutes the geological forecourt for the formation of a future cove. It has a circular shape with vertical walls and is currently connected to the sea, but it has not yet been completely engulfed by it.