The Trevi Fountain, one of the world’s most iconic landmarks, has captivated audiences in films from Fellini’s La Dolce Vita to Netflix’s Emily in Paris. Every year, millions of tourists navigate Rome’s narrow streets to marvel at the grand Titan god Oceanus, surrounded by cascading waterfalls that flow into the fountain’s striking turquoise basin.

Yet, few ever get a glimpse behind the magnificent baroque structure to see the intricate system that keeps the water flowing.

Tucked away behind wooden doors on a nearby street lies the control chamber managing the fountain’s water supply, fed by the ancient Aqua Virgo aqueduct, which stretches 16 kilometers (10 miles) to reach the city. Two electric pumps recycle 126 liters (33 gallons) of water per second, with Rome’s water management company, ACEA, overseeing the flow 24/7 to ensure its precision.

The delicate balance of water movement is crucial for the fountain’s visual effect, explained Davide D’Alonzo, ACEA’s regional manager. Even the slightest deviation in water levels could disrupt the display.

Inside the modern control chamber, metal tanks and illuminated panels manage the system, while the original arched chamber houses a rushing water pipe and an 18th-century hydrometer still used to measure water levels.

A large, weathered spreadsheet on the wall lists the names of affluent Roman families who once received water from this chamber—along with records of when their supply was cut off due to unpaid dues.

From the grated windows of the chamber, one can peer out at the bustling crowd gathered around the fountain, unaware of the hidden mechanics that sustain its beauty. Visitors eagerly toss coins over their shoulders into the water, following the legend that doing so will ensure their return to the Eternal City.