Underground Giants

Most people picture tall stone arches when they think of aqueducts. But here is the surprise: over 80% of Roman aqueducts ran underground. The iconic arched bridges were only needed to cross valleys.

• Aqua Marcia — stretched 91 km to bring cold mountain water to Rome in 144 BC
• Pont du Gard in France — a 49-meter-tall bridge section still standing after 2,000 years
• Aqua Virgo — still feeds the Trevi Fountain in Rome today

The underground channels were covered to prevent contamination and evaporation. Roman engineers understood water hygiene better than most medieval European cities would a thousand years later.