The Arcadian League was a federal league of city-states in ancient Greece. It combined the various cities of Arcadia, in the Peloponnese, into a single state. The league was founded in 370 BC, taking advantage of the decreased power of Sparta, which had previously dominated and controlled Arcadia.  Mantinea, a city that had suffered under Spartan dominance, was particularly prominent in pushing for its founding. The league had its capital at the newly founded city of Megalopolis, where an assembly of 10,000 met as its governing body.