Question

how brick
s were arranged to build walls in Harappan cities

Answer 1

Bricks were arranged In such a manner that they will stand perpendicular to land and their will 90° in the corners this was the special thing about the bricks and houses made in harappan city

Answer 2

Interlocking pattern of laying bricks was used while building walls in Harrapan cities.  
Ancient Indus valley civilization was known for the strength of its walls which stood strong for thousands of years.  
These bricks were watertight due to the presence of natural tar and coated with plaster for extra strength of the walls.