Amphitheater is located in the city area connecting the Castello district and the Sant'Avendrace area.
The term 'amphitheatrum' (amphitheater) designates a particular type of monument, peculiar to the Roman world and culture, intended to host gladiator fights (called 'munera') and ferocious animal hunts (called 'venationes'). The term seems to explicitly refer to the architectural form of the structure: it would be precisely an 'amphi-theatrum', that is, a double 'theatrum'. The term replaced, starting from the early imperial age, the older one of 'spectacula', which literally indicates a set of seats from
which it was possible to watch a show. The oldest evidence of this type of monument seems to date back to the end of the second century BC.
The construction of the Cagliari amphitheater dates back to between the first and second centuries AD. Its structure is largely excavated directly into the rock of the hill, both the steps and the underground environments. For the construction of the remaining construction parts, such as the destroyed S façade, local limestone, extracted in blocks, was used. The amphitheater area itself became over the centuries (starting from the Judicial Age) a real stone quarry, used both for the recovery of construction material already worked and for the extraction of new limestone blocks. The signs of this use of the area are still clearly visible. The systematic plunder ended around the mid-nineteenth century, when the amphitheater became municipal property.
During the excavation carried out by Spano, numerous marble slabs were found, intended to cover the steps, divided into three different levels, each of which was intended for spectators relevant to a specific social class; access to each level took place from a specific passage. The capacity seems to be around ten thousand spectators. Above the arena was the 'podium', reserved for the most important characters. The social classes of the free (hierarchically divided into 'senators, equites', plebeians and serfs) occupied the 'ima, media, summa cavea'. Women and slaves occupied the last covered staircase, the gallery.
The Cagliari amphitheater mainly used to fight between gladiators and clashes between gladiators and ferocious animals, but it seems that the amphitheater was also intended for the performance of theatrical performances and the execution of capital sentences.
The rainwater that collected on the steps of the amphitheater flowed into the cistern through a 96 m long passage accessed through an opening dug in the rock ('euripus') on the S side of the arena.

History of excavations 
The first information relating to the amphitheater dates back to the 17th century and is reported in a work by Dionisio Bonfant, actually dedicated to the events of the Sardinian saints. This was followed by a period of silence that was interrupted in 1823 by the captain of the Royal British Navy William Henry Smith, who, in his representation of the Bay of Cagliari, mentions the existence of the ruins of an ancient amphitheater, located near the Capuchin convent. Other news was reported by Abbot Vittorio Angius in 1836, by Valery in 1837 and by General Alberto della Marmora in 1840. However, it was only between 1866 and 1868 that the first excavations took place, conducted by Canon Giovanni Spano. The subsequent excavation, consolidation and restoration work dates back to 1937-38, conducted by the archaeologist Doro Levi.

Bibliography
P. Meloni, Roman Sardinia, Sassari, Chiarella, 1992;
S. Angiolillo, The Art of Roman Sardinia, Milan, Jaca Book, 1982;
P. Pala, The Roman Amphitheater of Cagliari, Nuoro, Insula, 2002;
A.M. Colavitti, Cagliari; The Herm of Bretschneider, Rome, 2003; A.M. Colavitti-C. Tronchetti, Cagliari Archaeological Guide, series “Archaeological Sardinia. Guides and Itineraries”, Sassari, Carlo Delfino, 2003;
A. Mastino, History of Ancient Sardinia, Nuoro, Il Maestrale, 2005;
M. Dadea, The Roman Amphitheater of Cagliari, series “Archaeological Sardinia. Guides and Itineraries”, Sassari, Carlo Delfino, 2006;
M. Dadea, “An Early Christian graffiti with the figure of a ship in Cagliari”, in The baptismal building in Italy. Aspects and problems. Proceedings of the VIII National Congress of Christian Archaeology, Bordighera, 2001, I, pp. 155-159.