Airborne LiDAR application to karstic areas: the example of Trieste province (north-eastern Italy) from prehistoric sites to Roman forts

The Trieste Karst, at the north-easternmost shore of the Adriatic Sea, is rich in prehistoric caves and protohistoric hill forts. Most of these archaeological sites were already identified in the second half of the 19th century when large parts of the area were almost without vegetation coverage for the effect of sheep breeding and exploitation of wood resources. Only a few open-air archaeological sites have been discovered in recent years due to the lack of systematic archaeological surveys and reforestation. Airborne LiDAR (light detection and ranging) data, originally acquired for environmental monitoring over the Friuli Venezia Giulia region (north-eastern Italy), have been recently analysed by means of free open source softwares for archaeological prospection of the Trieste Karst area. The LiDAR derived images have allowed identifying numerous unknown fortified structures ranging from prehistory to Roman time within a complex archaeological landscape that includes possible funerary barrows, agricultural terraces and other structures. The discovery of a probable Roman republican fort is particularly significant since similar structures, almost unknown in Italy, find comparison only with younger examples of military forts from Roman provinces. The discovery of prehistoric, protohistoric and Roman fortified sites reported in this paper shows that airborne LiDAR remote sensing represents a revolution in landscape archaeology and archaeological mapping of karstic areas. This technique can provide unexpected results even in relatively urbanized territories investigated for a long time.