Around 20-25% of the Friuli Venezia Giulia region consists of karstified rocks. The geological, geographical and climatic conditions have given rise to a whole series of karst landscapes which have developed in different ways from each other on limestone of different ages, located at different altitudes. One encounters splendid examples of alpine karst (Mt. Canin and Cansiglio-Cavallo Massif), mountain-hill karst (Mt. Ciaurlec, Julian Prealps) and marine coastal karst. In the Classical Karst near Trieste, the worldwide symbol of karst phenomena, over 3,000 caves are known while half a dozen are over 1,000 m in length. There are about eighty solution and collapse dolines with a diameter greater than 100 m.
