With a capacity of 20,000 seats approximately, it counts among the largest ancient theatres in Greece. Nestling in the southeastern side of the castle hill, so as to be linked to the agora, it overlooked the ancient city and was visible from the Argolic gulf.

In 125 AD Emperor Hadrian visited Argos and soon after an eighteen mile long aqueduct was built to provide the town with an ample supply of water (also for the functioning of its new baths). A square fountain was built in the agora; in origin its brickwork structure was covered with marble slabs; archaeologists found out that it had been turned into a small house.

After the construction of the aqueduct a circular temple built upon a sacred well was turned into a monumental fountain, which was depicted in coins issued by Emperor Antoninus Pius. Hadrian and the emperors who came after him wanted to be associated with these life-sustaining facilities; at Olympia, almost at the same time, Herodes Atticus, an adviser to Hadrian and Antoninus Pius built a large nymphaeum which was decorated with statues of members of the imperial family. The most monumental fountain of Argos was built at the site where the aqueduct reached the town near the upper end of the theatre; a colossal statue of Emperor Hadrian stood at the centre of the fountain; the emperor was portrayed as Diomedes holding the Palladium, the image of Athena which protected the City of Troy and which Diomedes stole together with Ulysses, thus paving the way to the fall of the city. All the hope of the Danaans (Trojans) and their confidence in beginning the war always rested on the help of Pallas. But from the time that the ungodly son of Tydeus (Diomedes) and Ulysses, the author of crime, dared to tear the fateful Palladium from its hallowed shrine, slew the guards of the citadel-height, and, snatching up the sacred image, ventured with bloody hands to touch the fillets of the maiden goddess – from that time the hopes of the Danaans ebbed and, stealing backward, receded; (Virgil - The Aeneid - Book II - Translation by H. R. Fairclough)

Nero's interest in this part of Greece was largely focused on the Games in which he competed. Hadrian did not neglect this aspect of Greek life, even if not personally inclined to participate. Pausanias happens to mention "the boys" race on the riding-track at Nemea". The event had died out there, he adds, but "the emperor Hadrian restored it to Argos for the Nemean winter Games". These games seem to have been held at Argos in later years on 30 December; it is reasonable to infer that Hadrian watched them, indeed presided, on this day at the end of 124. It is hardly necessary to comment that Hadrian's revival of a horse-race for boys admirably suits what is known about his tastes.