This is a standard view of the entrance to the Grotto di Napoli, which provided a road to Pozzuoli. Robert Adam noted that this was '... a road cut by the Romans for near a mile underground, is another of the many thousand convincing proofs of their grandeur'. (J. Fleming, Robert Adam and his Circle in Edinburgh & Rome, London, 1962, p.154). This drawing can be compared with that shown in Paoli's Avanzi Delle Antichita Esistenti a Pozzuoli Cuma e Baja, Naples, 1768, pl.VI, which also gives its history as well as a plan and section at pl.VII. The Antichita di Pozzuoli drawing is by Giovanni Battista Natali (1698-1765) and was probably made sometime around 1760; it shows very much the scene as Adam saw it. Natali's drawing shows the doorway opposite the memorial left out by Adam in his composition, which was conceived on a smaller scale.