common in all other centres of the Indus civilisation.
Fourth Stage: Lothal
Lothal was founded much later than the above three settlements. Construction
began here around 2100 BC during the Mature Harappan period. It had all the
features typical of the cities of the Indus civilisation. Its citadel was built on a
high platform, about 150 × 120 feet, and its brick wall surrounded both the
citadel and the lower town. The pattern of streets and alleys was the same as
that of Mohenjodaro and Harappa.
    The most unique feature of Lothal was its dock— a large basin,
measuring 770 × 120 × 15 feet in length, width and depth respectively.
Situated east of the city, its walls were made of hard bricks and had two
openings which are believed to have been sluice gates. Four large round
stones with holes in their middle were found at the bottom of the basin. They
might have served as anchors for ships which used this basin as a dock. A
raised platform between the basin and the city also seems to indicate that this
was the dock of a major port, an emporium of trade between the Indus
civilisation and Mesopotamia.
    Many tools, stone beads and seals were found in Lothal, among them the
famous ‘Persian Gulf seal’. Probably, Lothal not only served long-distance
trade but also supplied the cities on the Indus with raw material such as
cotton from Gujarat and copper from Rajasthan. This would explain why
Lothal was founded at a rather late stage when the demand for these raw
materials was at its height in Harappa and Mohenjodaro.
Prospects and Problems
The recent excavations at Mehrgarh show that in this area of Baluchistan
there was a continuous cultural evolution from the sixth millennium BC
throughout the subsequent four millennia. The discovery of several Neolithic
settlements in Baluchistan, including the oldest mound at Mehrgarh, has led
to the conclusion that the Indus civilisation was the outcome of an indigenous
evolution which started in the north-west of the Indian subcontinent. The
many settlements of the fourth millennium BC which have been excavated in
recent years provide added evidence      for this new hypothesis.