Before Spanish conquistador Hernán Cortés destroyed the Aztec capital Tenochtitlan in 1521, he marveled at its impressive size and wealth. In a letter to his king, he wrote that the city was as big as Seville or Cordoba back home. Tenochtitlan had boulevards, bustling markets, canals, courthouses and temples. The Aztecs didn't model their capital after a European city, but what Cortés saw was remarkably familiar. Recently, some theoretical scientists have started to find there are universal laws that shape all urban spaces. And a new study suggests the same mathematical rules might apply to ancient settlements, too.