Megalopoli is a town in the southwestern part of the regional unit of Arcadia, southern Greece. It is located in the same site as ancient M…Megalopoli is a town in the southwestern part of the regional unit of Arcadia, southern Greece. It is located in the same site as ancient Megalopolis. When it was founded in 371 BCE, it was the first large urbanization in rustic Arcadia. Its theatre had a capacity of 20,000 visitors, making it one of the largest ancient Greek theatres.