As seen in Harappa, Mohenjo-daro and the recently partially excavated Rakhigarhi, this urban plan included the world's first known urban sanitation systems: see hydraulic engineering of the Indus Valley Civilisation. Within the city, individual homes or groups of homes obtained water from wells. From a room that appears to have been set aside for bathing, waste water was directed to covered drains, which lined the major streets. Houses opened only to inner courtyards and smaller lanes. The house-building in some villages in the region still resembles in some respects the house-building of the Harappans.