What was the political structure of the Indus Valley Civilization? Did they have a king or some sort of democracy?

Because the
Dravidian (or Harappan) language has not yet been deciphered; there is no way to determine their
political structure, although the presence of two large cities with roads built on a grid, flush
toilets and other amenities plus large city walls for protection indicate that some sort of
political structure was present. Substantial public amenities and protective features could only
be built by means of an effective system of taxation; therefore the Dravidians apparently had a
system of taxation which one would naturally associate with a governmental structure. One can
only speculate as to its true nature; although it is doubtful that it was a democracy. Democracy
appears to have been a uniquely Athenian feature. The successors to the Dravidians, the Aryan
tribesmen of Eurasia, were organized into tribal units each ruled by a Rajah,
or chief who governed with the aid of a council of tribal elders. There were
apparently hundreds of these local tribal groups, each with its own rajah, but no centralized
government existed. Over time, the individual rajahs did attempt to extend their influence over
neighboring communities, most often by conquering them. Interestingly, the word rajah,
of Indoeuropean origin, is closely related to the Latin rex
meaning "king," and the origin of the words "regal" and "royal."
Although Indoeuropeans apparently influenced languages throughout the Eurasian continent, their
system of government (or lack thereof) did not extend beyond the Indian
sub-continent.