Ancient Romans were no strangers to spectacle, and their amphitheaters, like the Roman Colosseum, show just how much they liked a good blood-soaked show. Gladiators fought each other, prisoners of war, and wild animals like lions, tigers, ostriches and boars. But a lesser known combat spectacle was the naumachia, enormous staged naval battles.

A Roman naumachia, as imagined by Spanish painter Ulpiano Checa

The first recorded naumachia was put on by none other than Julius Caesar, in 46 BC, as part of “triumphs,” civil ceremonies, celebrating his victories in foreign lands. A basin in the Campus Martrius, an area of Rome by a bend in the Tiber River, was flooded and hosted a giant sea battle. As described in the University of Chicago’s Encyclopaedia Romana:

“There, ships of two, three and even four banks of oars representing the Tyrian and Egyptian fleets were set afloat, manned by four thousand oarsmen and, on each side, one thousand fighting men, all prisoners of war or condemned to death. Such was the novelty of the spectacle that people thronged the streets and camped along the roads to see it, many being killed in the crush to witness the death of others.”

Caesar’s heir and adopted son, Emperor Augustus held his own naumachia (the word could refer both to the event and the arena) in 2 BC on the banks of the Tiber River by the Tiber Island. Augustus’s naumachia was built in a enormous basin that measured 1800 by 1200 Roman feet (a Roman foot was very slightly smaller than a U.S. foot), and featured an island for wealthy spectators. The island was connected to the banks of the basin by a bridge constructed from 120 ft wooden beam from the largest tree ever witnessed in Rome.

An engraving of a naumachia, author unknown.

The largest of the naumachiae was hosted by Claudius to celebrate the partial draining of Lake Fucinus, and included 19,000 fighters and 12 triremes (a type of warship with three levels of oars) on each side. Given the enormous amount of condemned criminals battling in the spectacle, Claudius surrounded the lake with rafts of the elite Praetorian Guards, protected by ramparts and armed with catapults. Due to a snarky remark from Claudius being mistaken for a pardon, the criminals initially refused to fight, and required threats to get the contest going. After the battle, the massive outlet failed to drain as planned, and required further engineering, and another naumachia to celebrate (this time with gladiators fighting on pontoons).

Emperor Nero contributed his own naumachia in 57 AD, and in line with his historic reputation of excess and insanity, built a wooden amphitheater, covered with an enormous blue awning with stars to represent the night sky. His naumachia was stocked with fish, and would feature both sea battles, and after draining the theater mid-contest, land battles.

The Colosseum and its hypogeum in its current state. Credit: Flickr user rente42

The Flavian Amphiteater, more commonly known as the Roman Colosseum, also hosted naumachiae, as shown by evidence discovered by Heinz-Jürgen Beste of the German Archaeological Institute in Rome. Beste is an expert on the hypogeum, the labyrinth of masonry below the Colosseum’s main floor (built of wood and covered in sand). Here, in various tunnels, chambers and cages, animals and gladiators awaited their fates before contests. As reported by Smithsonian, Beste discovered what he believes to be runoff canals used to drain the amphitheater (it was filed by a nearby aqueduct). The sea battles in the Colosseum were smaller than other naumachiae, fought in water only three to five feet deep aboard scaled down warships.