Romans used tufa, a volcanic stone from Italy, and, by 2 BCE, travertine, a more durable alternative that resembled marble.

Romans added volcanic Italian sand to the recipe to mortar. This made the mortar very strong and durable, and it also allowed the mortar to set underwater.

Mortar, a combination of sand, lime and water in specific proportions, was commonly used to bond stones and hold them in place.

Tufa

Travertine