Ancient Roman architecture
Although concrete had been used on a minor scale in Mesopotamia, Roman architects perfected Roman concrete and used it in buildings where it could stand on its own and support a great deal of weight. The first use of concrete by the Romans was in the town of Cosa sometime after 273 BC. Ancient Roman concrete was a mixture of lime mortar, aggregate, pozzolana, water, and stones, and was stronger than previously-used concretes. The ancient builders placed these ingredients in wooden frames where they hardened and bonded to a facing of stones or (more frequently) bricks. The aggregates used were often much larger than in modern concrete, amounting to rubble.
Pozzuoli
The local volcanic sand, pozzolana (Latin: "pulvis puteolanus", "dust of Puteoli") formed the basis for the first effective concrete, as it reacted chemically with water. Instead of just evaporating slowly off, the water would turn this sand/lime mix into a mortar strong enough to bind lumps of aggregate into a load-bearing unit. This made possible the cupola of the Pantheon, which is still the world's largest unreinforced concrete dome.
The apostle Paul landed here on his way to Rome, from which it was distant. Here he stayed for seven days ("Acts" 28:13, 14) and then began with his companions his journey by the Appian Way to Rome.