The development of urban centers, script on seals, advancement of technologies and urban sanitation systems.
Explanation:
The development of urban centers, script on seals, advancement of technologies and urban sanitation systems are the features of the Indus valley civilization which make it unique in the history. They developed urban centers where people comes from surrounding areas for trade. They also used advance technology of measuring length and mass. They also formed the world's first known urban sanitation systems.
