The Carso is a long plateau facing SE-NW, sloping slightly downwards towards the west. The eastern part reaches about 400 metres in height, while the part nearest the Isonzo river is only around 100 metres above sea level. The plateau is formed of limestone, a rock made of calcium carbonate, which is eroded by rainwater made slightly acid by atmospheric carbon dioxide. This chemical action activated by rainwater is called “dissolution” and is responsible for the spectacular forms known throughout the world as “karst phenomena”. The term “karst” derives its name from the Carso of Trieste, as this was the first area of its kind to be studied by scholars from around the world, drawn by the geological features. The karst landscape is marked by the absence of surface water, as rainwater immediately infiltrates underground through the cracks in the limestone. Typical karst features include dolines, caves and potholes, while the micro surface features includes tiny grooves, holes and corrosion basins.