page_title: Posillipo
section_title: Seiano tunnel
hierarchical_section_title: Posillipo / Roman Monuments / Seiano tunnel
caption_attribution_description: English: Roman Seiano tunnel
context_page_description: Posillipo is a residential quarter of Naples, southern Italy, located along the northern coast of the Gulf of Naples.
  From the 1st century BC the Bay of Naples witnessed the rise of villas constructed by elite Romans along the most panoramic points of the coast, who had chosen the area as a favourite vacation spot. The remains of some of these as well as the Seiano tunnel can be seen today in the Parco archeologico del Pausilypon, or Posillipo Archaeological Park, and elsewhere.
context_section_description: The extraordinary 770 metre-long tunnel of the "Seiano cave" passes beneath the Posillipo hill and connected the imperial villa and other patrician villas nearby with the Phlegrean Fields and the towns and ports of Puteoli and Cumae. It owes its name to Lucius Aelius Seianus, prefect of Tiberius, who according to tradition commissioned its enlargement in the first century AD; the first tunnel was built 50 years earlier by architect Lucius Cocceius Auctus at the behest of Agrippa. 
  The eastern entrance is cut into the rock cliff within the archaeological park while the western entrance was a monumental arch with opus reticulatum lining the cliff sides, and both ends being of about 14 m height.
  The height, width and length of the tunnel made it a great engineering achievement and an extravagant one considering it served only a small population. An enormous volume of rock alone had to be removed though some served as building material for the villas. The tunnelling was complicated by the alternation of pozzolanic earth with tufa necessitating the elaborate lining of most of the tunnel with stonework of opus reticulatum and then with vaulting on top of these walls. Work progressed at 5–7 m per day as indicated by the joints between sections. It was not perfectly straight in plan but included small deviations near the centre where the tunnellers from each end met after remarkably small inaccuracies of alignment given the techniques of the time. It had three secondary side tunnels ending in openings overhanging the bay to provide light and ventilation.
  Although known about by scholars (for example it is referred to in the Polish writer Adam Mickiewicz's epic 'Pan Tadeusz' published in 1834), it had fallen into disuse over the centuries. it was rediscovered during works for a new road in 1841 and immediately brought to light and made passable by Ferdinand II of Bourbon, becoming a tourist destination. Additional lining and arches were built to repair and reinforce the ancient walls. During the Second World War it was used as an air raid shelter for the inhabitants of Bagnoli; the war and landslides during the 1950s took it back to a state of neglect since when it was restored.
caption: Seiano tunnel eastern end
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