Towering limestone cliffs rise above the turquoise waters of southern Thailand as we prepare to step off Ton Sai Wall. The jungle clings to the rock face while the Andaman Sea opens wide beneath us, ...

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 ...