Its site and function as a port forced most authorities to argue that it was either built by the Harappan trading communities that came by sea from the mouth of the river or may have been built by traders crossing the road on land. The site is surrounded by a mud brick dock. Unlike the defensive walls at Harappa and Mohenjodaro, the wall at Lothal included the area of workers as well as the citadel. The presence of a ‘dry shipyard’ and a warehouse distinguish it further from other major Harappan sites. The excavations have here revealed a tidal shipyard (with a complex door lock system) at its top. This was probably one of the most important ports on the Indian subcontinent. The Sabarmati River, which runs further ahead here, connected the dock to the Gulf of Cambay. The seals found at the site suggest that trade may have been conducted with the civilizations of Mesopotamia, Egypt and Persia.
The ‘dry shipyard’ is located along the eastern wall of the city and has the average dimensions of 214 m of 36 m. A 1 m wide gap in the north side is assumed to have been the entrance by which the boats entered the dock. While a weir on the south has allowed the excess water to overflow. The town though, which is wider at this point than elsewhere, may have been a dock for unloading. The excavations of the warehouse revealed ample evidence of trade which was clearly the basis for the existence of Lothal. The construction, at the southwest corner of the wharf, caused a 4 m high platform of blocks of cubic mud to rise, the gap between them allowing ventilation. Over 65 Indus Valley seals have been discovered that show the images of packing material, bamboo or rope, suggestive of the importance of trade to the community. There were also discoveries of pottery, semi-precious stones, pearls and even necklaces made of tiny golden pearls. The rice and millet were clearly in use and there is some evidence that the horses had been domesticated.
Archaeological excavations show a planned city in a grid, with underground drainage system, wells, brick houses with baths and fireplaces. The brick-raised deck to the southeast may have been an oven where the seals and plaques were burnt and hardened. Found items include painted pottery, ivory, shells, semi-precious stone items, pearls, bracelets and terracotta toys. The long rectangular tank to the east may have been used as a dock. The discovery of a Bahrain seal suggests that it was a flourishing centre of foreign trade. The cemetery to the northwest had large funerary ships indicating grave burials. The archaeological museum at the site shows the fragments of this well-ordered civilization.