Long ago, when Romans wanted to build a new temple, they would head to the nearby quarries of Tivoli, chisel out blocks of porous rock called lapis tiburtinus — now known as travertine — and float the cargo downstream on rafts to craftsman in town.
That’s how they made the Colosseum 2,000 years ago. That’s how they made St. Peter’s Basilica and Bernini’s great colonnade hundreds of years later.
