The Nymphaeum divi Alexandri, monument known as "Trophies of Marius," is a fountain of ancient Rome, the remains of which are preserved in the northern corner of the Piazza Vittorio Emanuele II in Rione Esquilino.
The monument was originally located at the confluence of the Via Tiburtina or via Collatina with the way Labicana. This position he influenced the plan, trapezoidal in shape.

The building is a monumental fountain (nymphaeum) with function display terminal (munus) and water distribution castle (castellum aquae). It is made in the final stretch of a branch of the aqueduct coming from the Porta Tiburtina (Porta San Lorenzo) to head towards the Esquiline. The arches of this branch, some of which are still visible between the square and Pepe via Turati, can be identified only with the Claudian aqueduct or the Anio Novus reasons for elevation.

From the fountain sculptures come from the two trophies that since the Middle Ages gave the property of their traditional name of "Trophies of Marius," since 1590 placed on the balustrade at the top of Cordonata that goes to the Capitol. The sculptures, erroneously attributed to Gaius Marius in the victories over the Cimbri and the Teutons, are datable and Domitian were erected after the victorious campaigns against the Chatti and Dacians in 89.

The monumental structure (volume approximately 4000 m³; bottom width 25 m) occupies the highest part of the Esquiline and it's all in brickwork originally covered in marble, as evidenced by the numerous holes distributed over grappa up. It is built on three levels with different environments and channels are still visible. The water was placed on the third floor on the right rear side of the structure at a considerable height from the ground (9.85 m); after passing a massive central semicircular, was divided into two parts and was then conveyed to five channels of earthenware covered in a tank which no longer exists on the front of the fountain. From here, through tubes placed inside the walls, the water was collected in a second tank covered with earthenware and divided into niches alternately rectangular and arched. A third tank attingimento, partially preserved, collected water back downstairs for the supply of altimetrically lower areas of the city.

Sole survivor of the fifteen-show fountains of ancient Rome, the Nymphaeum of Alexander, to the mole and the spectacular effects of grandiose space, it can be considered the forerunner and the inspiring model of major exhibitions of water from the late Renaissance and the Baroque (eg. Trevi Fountain, Fountain of the Acqua Paola on the Janiculum). For this attracted the attention of many scholars as early as the sixteenth century (Étienne Duperac, Sallust Giovanni Peruzzi, Pirro Ligorio) that they provided sometimes fanciful reconstructions, while in 1761 the Piranesi dedicated a monograph with numerous engravings that illustrated faithfully the state of conservation of the ruin.