The Ludus Magnus or The Great Gladiatorial Training School is the largest of the gladiatorial arenas in Rome, Italy. It was built by the emperor Domitian (81-96 AD) in the valley between the Esquilino and the Celio, an area already occupied by Republican and Augustan structures. The still visible ruins of the monument belong to a second building stage attributed to the emperor Trajan (98-117), where the Ludus plane was raised by about 1.5 m. The remains of the complex were discovered in 1937, but only 20 years later excavations were terminated. The name and construction period of Ludus Magnus are known, thanks to antique sources. There is also its blueprint that was found among some fragments of the marble city plan ( Forma Urbis) drawn in the Severian age (early third century AD). However, there were great doubts about where it was located in the general topography of ancient Rome, so that it can now be related to a building in Piazza Iside, still visible. The Ludus Magnus was located in this area as it was built for the performances to be held at the Flavian Amphitheatre (the Colosseum). To facilitate connections between these two buildings, an underground gallery linked the two buildings. The path, with an entrance 2.17 m wide, began underneath the amphitheatre and reached the Ludus at its southwestern corner. At the centre of the Ludus Magnus, built on two levels, there was an ellipsoidal arena in which the gladiators practiced. It was circumscribed by the steps of a small cavea, probably reserved for a limited number of spectators. The cavea had a four-sided portico (of about 100m per side) with travertine columns. It led to a number of outside rooms, to be used by the gladiators and as services for the performances. Only a few ruins in Travertine remain of the colonnade which was raised in the place where the columns were probably located originally. In the northwest corner of the portico, one of the four small, triangular fountains has been restored. It lies in the spaces between the curved wall of the cavea and the colonnade. A cement block remained between two brick walls, converging at an acute angle. A large part of the brickwork structures were originally covered by marble slabs that were later removed. The entrances to the Ludus Magnus were built on the main axes. The one at via Labicana, at the center of the building’s northern side, was probably reserved for important people, since a decorated place of honour was found on the cavea. The life of Ludus Magnus ended, as did that of the Flavian amphitheatre, with the end of gladiator performances. Before the middle of the sixth century, the area was no longer cared for and numerous churches were built, as the population continued to decrease.