The first known naumachia is organized in Rome by Julius Caesar in 46 BC for his quadruple triumph.
After digging a large basin near the Tiber, in the Campus Martius, which holds true BIREME, galleys and quadriremes, recruited among prisoners of war fighters in 2000 and 4000 rowers.
In 2 BC, for the inauguration of the temple of Mars Ultor, Augustus gave a naumachia that emulate those of Caesar. As he himself points out in Res Gestae, dug on the right bank of the Tiber, in the place called "Forest of the Caesars" (nemus Caesarum), a reservoir where s'affrontarono 3000 men, besides the rowers, of 30 vessels with rams, and many smaller units.
The fighters were sentenced to death and we know that naumachiarii (fighters in naumachia) before the battle the Emperor greeted with a phrase that became famous: Morituri te salutant.

The Naumachia best known is that of Augustus it had to be around 533 x 355 m. Pliny says that the center of the basin, most likely a rectangular shape, was an island connected by a bridge embankment.
The basin must have a depth of 1.5 m, the minimum to allow the ship to float, and therefore a capacity of 200,000 m3: the aqueduct Alsietina, specially built by Augustus for his power, he could fill in 15 days and a navigation channel that provided access to ships coming from the river, crossed by a drawbridge.

Considering the size of the basin and those of a trireme (35 m x 4.90 approx), the thirty vessels used should not have much room for maneuver on the water. Moreover, knowing that the effect of a Roman trireme was about 170 rowers and one of the 50 or 60 soldiers aboard, a quick calculation leads to the conclusion that to reach a figure of 3,000 men, the ships had to take the of Augustus naumachia many more fighters a real fleet.
A large pipe discovered on the slopes of the Gianicolo hill above the Church of St. Cosmas is the first archaeological evidence on the location of naumachia. Another hypothesis about the exact location of the monument situated between the Via Aurelia in the north and the church of San Francesco a Ripa in the southeast, at a bend in the Tiber. The viaduct Republican on the Via Aurelia near San Crisogono could be served by the spillway for the reservoir.