How They Were Built

Roman aqueduct engineering was astonishing for its era. Surveyors laid the gradient with leveling tools accurate to a few centimeters per kilometer — essential because water flowed by gravity alone, and too steep a slope eroded the channel while too shallow caused stagnation. The Aqua Claudia outside Rome drops only 0.15% across its 69-kilometer run.

Where terrain fell away, Romans built stone arches, some over 30 meters tall. Where it rose, they drove tunnels through solid rock — sometimes working from both ends simultaneously and meeting in the middle with errors of less than a meter. The aqueducts were built to last centuries, and many lasted millennia. Modern infrastructure rarely targets that kind of time horizon.