In an underwater recovery operation off the coast of Bacoli in southern Italy, archaeologists have uncovered a Roman-era breakwater constructed from recycled architectural materials — a find that sheds light on ancient Roman maritime engineering.

The submerged remains were discovered at Portus Iulius, the Roman naval base at Misenum, formerly the headquarters of the Classis Misenensis, the Roman Empire’s dominant fleet in the Tyrrhenian Sea. It is the same fleet that was commanded by Pliny the Elder during the eruption of Mount Vesuvius in 79 CE.