Water

ROMA – Anfiteatro Flavio e Colosseo con la meta sudante
Flavian Amphitheater and Colosseum with the Meta Sudans
Publisher: F. Fichter, Rome

Google Street View.

The Flavian Amphitheatre, more commonly known as the Colosseum, stands in the archaeological heart of Rome and welcomes large numbers of visitors daily, attracted by the fascination of its history and its complex architecture. The building became known as the Colosseum because of a colossal statue that stood nearby. It was built in the 1st century CE at the behest of the emperors of the Flavian dynasty. Until the end of the ancient period, it was used to present spectacles of great popular appeal, such as animal hunts and gladiatorial games. The building was, and still remains today, a spectacle in itself. It is the largest amphitheatre in the world, capable of presenting surprisingly complex stage machinery, as well as services for spectators.
Parco archeologico del Colosseo

Parco archeologico del Colosseo online resources

The Meta Sudans was a large monumental conical fountain in ancient Rome. The Meta Sudans was built some time between 89 and 96 under the Flavian emperors, a few years after the completion of the nearby Colosseum. It was built between the Colosseum and the Temple of Venus and Roma, close to the later Arch of Constantine, at the juncture of four regions of ancient Rome: regions I, III, IV, X (and perhaps II). A meta was a tall conical object in a Roman circus that stood at either end of the central spina, around which racing chariots would turn. The Meta Sudans had the same shape, and also functioned as a similar kind of turning point, in that it marked the spot where a Roman triumphal procession would turn left from the via Triumphalis along the east side of the Palatine onto the via Sacra and into the Forum Romanum itself.
…
Photos from the end of the 19th century show a conical structure of solid bricks next to the Arch of Constantine, surrounded by its own original, reflecting stone pool. The ruins of Meta Sudans survived until the 20th century. In 1936 Benito Mussolini had its remains wantonly demolished and paved over to make room for the new traffic circle around the Colosseum.
Wikipedia.