This fourth volume (Proceedings 4) presents the results of an international conference held at the Museo de los Origenes (Casa de San Isidro) in December 2008. The work is divided into three parts: First general aspects of the rock world' in the Iberian Peninsula are surveyed, including the chronology of man-made caves, the Classical background to cave-dwelling, and the chronology of rock-cut tombs. The second part presents eleven studies of specific regions and rock complexes' in the Iberian Peninsula ( San Vitor', in San Lorenzo da Barxacova, Parada del Sil, Ourense; El Bierzo'; the upper valley of the Ebro; San Martin de Albelda', in La Rioja'; the middle valley of the Cidacos river; the high valley of the Arlanza river; San Frutos del Duraton', Segovia; the suburbium and territory of Ercavica in Late Antiquity and Early Middle Ages; the territory of Sierra Magina; and finally, the Almagruz caves, in Purullena, Granada. The third part examines parallels in other Mediterranean regions, such as the rock city' of Matera (Italy), the valley of the Euphrates (northern Syria); the churches built on the rock of Lalibela (Ethiopia), and the rock world' in the provinces of 'Arabia' and Palestina Tertia in Jordan."