The Harappans used

bricks to build their cities.

They used standardized brick sizes of 1 * 2 * 4 (10 x 20 x 40 cm)

Explanation:

Harappa masonry areas spread around a central depression that could represent a reservoir or reservoir. Likewise, each mound is surrounded by massive brick walls with paved aisles. The front door was only 2.8 meters wide, but that was enough for the cars to pass.