Indus Valley civilization was mainly an urban culture sustained
by surplus agricultural production and commerce, the latter including trade
with Sumer in southern Mesopotamia. Both Mohenjo-Daro and Harappa are generally
characterized as having "differentiated living quarters, flat-roofed brick
houses, and fortified administrative or religious centers." Although such
similarities have given rise to arguments for the existence of a standardized
system of urban layout and planning, the similarities are largely due to the
presence of a semi-orthogonal type of civic layout, and a comparison of the
layouts of Mohenjo-Daro
