The Napoli Sotterania is situated in the centre of Naples 30 metres below the surface. It is a series of underground tunnels dug out from soft tufo stone and covers most of the city. The moister levels are as high as 70% and it is possible to grow plants down there without having to water them (aslong as there is a light). The tunnels were used as air raid shelters during the wars and drawings of bombs and planes and echted into the walls depicting the suffering of that period. During some of the tour you have to use candlelight which was quite exciting. Very impressive.