Herodes Atticus was not an ordinary visitor. A Greek-born Roman senator, scholar, and friend and teacher to emperors, he arrived at Olympia in the mid-2nd century AD with his wife Regilla — who had to be specially designated an honorary priestess of Demeter just to enter the site, since women were ordinarily excluded. When the couple experienced the water shortage firsthand, Herodes made a public promise: he would pay for an adequate water supply out of his own fortune. By the next Olympiad — four years later — the Nymphaeum bearing his name had been completed.

The structure he commissioned was called a nymphaeum, the standard Mediterranean name for an ornate terminal building at the end of an aqueduct. The name meant 'home of the nymphs,' the water goddesses of Greek tradition. This one, however, was above all practical. It received water from a new aqueduct into a cistern, then released it in stages through a network of open and concealed channels running throughout the sanctuary. Long troughs lined the sides of every playing field, so that athletes and spectators could dip their small drinking bowls — called paterae — directly into flowing water rather than queuing at a well.

The engineering challenge was substantial. The sanctuary at Olympia sat at roughly 35 to 50 meters in elevation, and the local rivers were either insufficient or too calcified from limestone to be drinkable — the Alpheios, the larger of the two rivers flanking the site, was so hard with dissolved carbonates that it was useless for drinking water. What Herodes' engineers needed was a higher-elevation freshwater source some distance from the site.

Archaeologists excavating the nymphaeum in 1877 and 1878 initially thought they had found a spring capture in the hill behind the structure. But the more they dug, the more complex the system became. They discovered a brick-lined tunnel, 88 meters in visible length, running east through the base of Kronion hill along the treasury terrace and then into the hillside, mounted atop a buttressed wall for both stability and elevation control. The visible portion drops from 55 meters at the hill entrance to 50 meters at the cistern — a modest but sufficient 5-meter gradient that would have sent water jetting impressively from the nymphaeum's spouts. Where that tunnel ultimately originated is still debated by scholars, but the best evidence points toward the Erymanthos River some 15 kilometers to the east, or to the municipal water system of ancient Pisa, which had likely already tapped mountain sources well above Olympia.

Once the cistern received water, the distribution network spread it everywhere. Publicly accessible troughs ran along the open areas. Hidden pipes ran through walls to wherever public access was not desired. The system fed newly constructed Roman-era baths and the swimming pool of what was apparently a grand hotel. Most importantly, those long drinking troughs beside every field transformed the experience of being at the Games.

Before Herodes, the 1st century had already seen Olympia become an international spectacle — Roman emperors competed, or sent competitors, and the site expanded greatly to accommodate the crowds. The stadium was moved; the palaestra was relocated. But the water infrastructure had never kept pace. Nine wells requiring manual lifting, a few short gravity channels from a muddy river — that had been the sum of it, across centuries of the world's most celebrated athletic festival. Herodes Atticus, in a single building campaign, ended Olympia's dependence on those inadequate local sources and brought fresh mountain water to every corner of the sanctuary.

The nymphaeum was excavated in the 1870s, but the road built through the site around 1886 cut through the hillside above the tunnel, removing evidence of where exactly the aqueduct entered the hill. The visible structure today consists of the main curved wall with its semicircular apse and the remains of the cistern behind it — enough to convey the scale of what Herodes built, if not its original grandeur. Statues once stood along the facade, several of them carrying paterae in one hand, gesturing at the structure's primary purpose.

The building is late in the story of ancient Olympia — a Roman addition to a sanctuary that had existed for more than a thousand years. But it was arguably the most impactful single intervention ever made to the physical comfort of the site. The generations of spectators who had suffered the summer heat without adequate water, carrying their own jugs across the grounds of the most sacred athletic site in the Greek world, would have found the running troughs almost miraculous.