Puteoli (now Pozzuoli) was a major Roman port. It was sheltered by the most famous arched breakwater. This breakwater was buried under the modern breakwater (!) but it was still visible in the 19th c. and known as “Molo Caligoliano”:


Puteoli breakwater fresco at Villa Stabiae, Pompei (1st c.)
(source: http://www.marine-antique.net/Port-de-la-maison-de-Stabie-Pompei)

“Il Designo Bellori”, drawing by Pietro Santi Bartoli after a 3rd c. fresco found at Esquilino (Rome) (now vanished) and published by Bellori in 1673.
(source: http://www.vesuviolive.it)

Puteoli breakwater on a souvenir glass flask known as Fiascetta di Populonia and showing the pilae (4th c.)
(source: http://www.archeoflegrei.it/i-souvenir-di-puteoli/)
Puteoli breakwater on a souvenir glass flask kept at the National Museum of Prague and showing the pilae (4th c.)
(source: https://web.uvic.ca )
See also: Picard, C. (1959) « Pouzzoles et le paysage portuaire », Latomus, T. 18, Fasc. 1, pp. 23-51.


Castrum Puteolanum in the 17th c. (?) (detail)
(source: http://www.archeoflegrei.it/i-castra-flegrei/)

Puteoli breakwater after Paoli (1768)
(source: http://www.archeoflegrei.it/portodiputeoli/)

Puteoli breakwater after Hamilton (1776)
(source: https://commons.wikimedia.org/wiki/File:Willi

Puteoli breakwater after Smargiassi (ca. 1840)
(source: http://www.artvalue.com/)

Puteoli breakwater after Leitch (1840)
(source: http://www.antiquemapsandprints.com)

It can be seen from the dates of these pictures that the structure was gradually destroyed.

Paolo Antonio PAOLI, provided the dimensions of the ancient arched structure in his “Antichita di Pozzuoli” in 1768 (with some later editions).

Puteoli arched breakwater according to Paoli (1768) (source: http://www.archeoflegrei.it/portodiputeoli/)

The drawing shows 15 pilae (including 2 supposed pilae). The largest pilae of ca. 15 x 15 m are at the offshore end of the structure. The nearshore pila is somewhat smaller: ca. 8 x 12 m. The opening between adjacent pilae varies from 0.7 to 1.0 pila width, which is close to the values found for the arched breakwaters of Portus Iulius and Misenum.