Megalopolis (“Big City”) was set up by the Theban general Epameinondas in a few years (371 – 368 BC) in his pursuit of containment of the Spartans, as well as Messene and Mantineia. The new residents of Megalopolis were partly taken from the larger Arcadian centers Tegea and Mantineia, and partly from nearly 40 smaller towns, which were sometimes completely abolished, and sometimes allowed to continue in a greatly reduced state. Megalopolis was the capital for the Arcadian League, with a federal council of 50 members and a larger general assembly, known as “the Ten Thousand” and assembled in the Thersileion. At its peak, the city must have been very large, given the enormous theater that it has housed. In 223, after several unsuccessful attempts in the decades before, the city was taken by the Spartans and destroyed, with a large proportion of the population escaped to Messenia under the leadership of Philopoimen, and returned a few years later turn around. In the time of Pausanias, the city has now fallen seriously into decline and would only continue to decline. In the middle ages, the city was finally abandoned, only to be restored after Greek independence.

The most important inhabitants of Megalopolis were Philopoimen (253-183 BC), an idealistic statesman and strategist, and the writer-statesman Polybios (208-122 BC), who was originally a political prisoner to Rome transported (as 1 of the 1000 hostages of the Achaeic League), but there he emerged as an adviser to, among others, Cornelius Scipio Africanus (junior), who would make Rome world power after the definitive destruction of Carthage (and Corinth). The preserved History of his works are of great importance for our knowledge of the history of Rome between 250 and 150 BC.

The archaeological site is especially worth seeing because of the theater, the largest in Greece, with around 21,000 seats and originally 50 rows of seats (of which the lower rows with the seats for the significant are still reasonably preserved) and the Stoa of Philippos (which by the way, was not built by the father of Alexander the Great, Philippos of Makedonia, but only got his name from the flattery of a Megalopolis-minded Makedonian in the 4th century) on the other side of the river. Of the buildings mentioned by Pausanias (including the aforementioned Thersileion (a huge colonnade, with a wooden roof supported by 67 marble columns, intended as a meeting room for “the 10,000” (their number would have been around 6000 in view of the space for seats) ), but already destroyed by the Spartans in 223) is hardly visible anymore, partly because the Helisson River (which ran through the city) has shifted its bed several times, among other things the large temple of Zeus the Savior has partially disappeared into the water, along with other buildings of the agora, of the city walls that have been around 9 km long, only a few sparse remains can be found, and the scarce finds from the city can be seen in the museum of Trípoli Restoration work on the antique monuments has been started, but hardly ever progressed.The location and atmosphere are largely determined by the clouds of smoke of the slightly power plant located below.

The modern town of Megalopolis is a small mining town nowadays just over 5000 inhabitants, which has been hit several times by severe earthquakes, and contains no sights, although it contains some churches, schools and nice squares. The power plant at Megalopolis deprives the city of its already few grandeur.