Also known as Grotta di Pozzuoli or Crypta Neapolitana, the grotto is an ancient Roman tunnel 700 metres long, built by Marcus Cocceius Nerva in 37 A.D., which passes beneath the hill of Posillipo and connects Naples with the Phlegraean Fields, before reaching the ancient town of Pozzuoli, further west along the coast. Narrow yet lofty, the tunnel was a marvel of ancient engineering. The tomb of the poet Virgil was also to be found there, though not visible in this view, creating a site that no cultivated visitor could miss. The grotto was depicted by numerous artists both before and after Wilson, including Gaspar Vanvitelli, John 'Warwick' Smith, Thomas Jones, Francis Towne, Hubert Robert and Claude-Louis Chatelet.