All the structure of the Fountain of the Rivers by Bernini supports the Egyptian Obelisk originally placed in the circus of Massenzio;
on the flanges of the reef are dressed the personifications of the four rivers realised by the collaborators of the maestro: the Danube of Raggi, the Ganges of Poussin, the Rio della Plata of Baratta and the Nile by Fancelli. In addition to these anthropomorphic figures, symbol of the four continents at that time known, the circular tank is populated by lions and other fantastic animals, while at the top of the fountain of the four rivers, was placed a bronze hen pigeon, symbol at the same time of the peaceful work of the Church in the world, and of the family of the Pontiff who wanted the monument: the Pamphili.
The tradition wants that the placement of the statues of the Nile and the Rio della Plata in the fountain, such as those of the statue of Sant'Agnese in the base of the right belfry of the front homonym church, are due to the rivalry between the two main architects of the time: Borromini and Bernini.
The Rio della Plata would have the hand raised to protect itself from the collapse of the fašade of the Church of Sant'Agnese in Agone
while the Nile would have the head veiled, not to allude the fact that the places of the sources were still unknown, but for the refusal to see the work of Borromini; in the same way the inhabitants of Rome are seeing, on the gesture of Sant'Agnese, who is touching his breast with the hand, the insurance that Borromini himself wanted to give concerning the fact that his church would not have collapsed.