What is one charactristic of the advanced culture of Harappan civilization

The ancient city of Harappa was considered to be advanced during its time due to multiple characteristics such as: the sheer size of the city (known today as urban); a large network of trade/commerce/transport technology and economy; accuracy of their measurement systems for length and mass; their use of measurements in architectural design, sewerage and drainage systems; innovative metallurgy techniques and manipulation of precious metals (lead, tin, bronze, copper).