The rocks composing the coastline between Masua and Cala Domestica are some of the most ancient of Italy dating back, even paleontologically, to the beginning of the Cambrian

(about 540 million years ago). In their geologic evolution they have been involved in two remarkable orogenetic processes, being also affected by different types of tectonic folds and distortions. The natural monument takes its name from the wild creek set between high and steep rock walls, where the natural geological environment offers a summary of the geological events that have occurred in this archaic territory. Are easily identifiable to the nacked eye the different stratifications of sandstones, striped dolomite and shales, as a result of the deposit activity of sediments by the seawater.These rocks (except for dolomites) contain the rests of peculiar index sea fossils that lived only in the Palaeozoic era: Trilobites (Arthropods) and Archaecyathan. In the creek of Canal Grande  opens the cave of the same name, a ravine dug by the sea into the insertions of sandstones and limestone, 151 meters long, about 30 meters high and 5 meters wide. All over the coastline it is possible to see numerous rocky ravines, fumaroles and semi-submerged alcoves. An amazing moment is when Mistral wind blows and the rough sea enters in the cave.