The Grotto of Pausilipo, Kingdom of Naples, c 1760.

Hand-coloured etching by Peter Fabris (active 1768-1779) and taken from from William Hamilton's (1730-1803) studies of Italian volcanoes, 'Campi Phlegraei' (published in Naples, 1776). Image represents the entrance to the Grotto of Pausilipo (now known as Posillipo) on the road between Naples and Puzzoli. The road, which is about 2400 feet long and 22 feet wide, was cut through a mountain of tender volcanic stone, or 'tufa'. Based on letters to the Royal Society in London, Hamilton's book was a seminal work on the nature and effects of volcanic activity.