The Vedic period in India began around 1500 BC with the arrival of the Aryans through the Khyber Pass from Central Asia. The nomadic Aryan settlers moved into the Gangetic plains and adopted an agrarian lifestyle. Their villages consisted of circular thatched huts made from bamboo and timber. Over time, the huts evolved rectangular plans with barrel vaulted roofs to overcome limitations of the circular design. Villages were arranged in clusters around an open courtyard or sacred tree.