The geological setting of the Neapolitan area, dominated by the volcanic districts of Campi Flegrei and Somma-Vesuvius, has played a fundamental role in the urban development since historical times. The volcanic materials emplaced by the two districts have been widely used in the Neapolitan architecture - as dimension stones, building stones and for the production of plasters - due to their great availability and overall good physic-technical properties. While the particular geology of the area has many positive aspects, it nonetheless includes several geo-hazards which have also had a deep influence on the historical evolution of the urban settlements. The numerous aspects of such a link between geology and anthropic activities in the Neapolitan area are here thoroughly investigated.