The Crypta Neapolitana is an ancient Roman tunnel near Naples. It was built in 37 BC, and is over 700 metres long.
The tunnel passes beneath the Posillipo hill and connects Naples with the so-called Phlegrean Fields and the town of Pozzuoli along the road known as the via Domiziana.
The eastern Piedigrotta entrance is now enclosed within an archaeological park, and the site of the villa of Vedius Pollio, and later imperial villa. The site is also noteworthy for the presence of the so-called Virgil's tomb, as well as the tomb of the Italian poet Giacomo Leopardi. Three secondary tunnels end in openings overhanging the bay, providing light and ventilation.
The name Grotta Seiano (Sejanus's cave) comes from the infamous Lucius Aelius Sejanus, prefect of Tiberius, who according to tradition, commissioned its enlargement in the first century AD. The first tunnel was built by the architect Lucius Cocceius Auctus for Agrippa during the civil war between Octavian and Sextus Pompeius in c.37 BC to connect the villa of Vedius Pollio and other patrician villas of Pausilypon (ancient Posillipo) to the ports of Puteoli and Cumae. The tunnel is one of a number of such works in the Naples area built by Cocceius.
The tunnel was still in use as a roadway until superseded by two modern tunnels in the early 20th century, and shows extensive restoration done by the architects of the Bourbon dynasty of Naples. During the Second World War it was used as a bomb shelter for the inhabitants of Bagnoli; the war and some landslides during the fifties put it back into a state of neglect. Today it has been restored as an archaeological site.
References:The Walls of Constantinople are a series of defensive stone walls that have surrounded and protected the city of Constantinople (today Istanbul) since its founding as the new capital of the Roman Empire by Constantine the Great. With numerous additions and modifications during their history, they were the last great fortification system of antiquity, and one of the most complex and elaborate systems ever built. They were also the largest and strongest fortification in both the ancient and medieval world.
Initially built by Constantine the Great, the walls surrounded the new city on all sides, protecting it against attack from both sea and land. As the city grew, the famous double line of the Theodosian Walls was built in the 5th century. Although the other sections of the walls were less elaborate, they were, when well-manned, almost impregnable for any medieval besieger.