The spring, also known as the Exedra of Herodes Atticus, one of the most opulent and impressive constructions inside the Altis, was situated between the temple of Hera and the treasury terrace. It stood at the end of a much-needed supply of pure drinking water brought to Olympia in AD 160 from springs east of the sanctuary and distributed by a dense network of pipes. Prior to that, water came from wells and was in short supply, especially during the Olympic Games when thousands of visitors flooded the sanctuary.
The monumental spring comprised two tanks backed by a two-storeyed apse, which rose to a half-cupola. The apse (16.62 metres in diameter) was of brick with polychrome marble revetment and had two tiers of eleven niches each, which held statues of the families of Antoninus Pius (lower tier) and of Herodes Atticus (upper tier). The central niche of each tier contained a statue of Zeus. Inside the apse was a large semicircular water tank. A marble bull, now on display at the Olympia Archaeological Museum, stood in its middle; it bore an inscription recording that Herodes dedicated the reservoir and its statues to Zeus in the name of his wife Regilla who was a priestess of Demeter Chamyne. An oblong basin, 21.90 metres long and 3.43 metres wide stood in front of the semicircular tank. At each end of this lower tank a small circular Corinthian temple, 3.80 metres in diameter, enclosed a statue; these represented Herodes Atticus and Antoninus Pius or Marcus Aurelius. Several of the monument's statues are displayed in the museum.
The monument is in a poor state of preservation. Almost none of the polychrome marble revetment has survived, while several pedestals and architectural members were re-used in the construction of the fifth century AD Christian basilica. However, illustrative material helps the visitor to visualize its great opulence.