The Roman aqueduct at Segovia, built around the first century AD without mortar, still carried water into the 1970s, its 167 granite arches held together by not... (opens in new tab)

The Aqueduct of Segovia delivered drinking water to a Spanish city for nearly nineteen centuries using nothing but precisely cut granite blocks held in place by their own weight. It was finally retired in 1973 — not because it failed, but because car exhaust was eating the stone.