<P> Mohenjo - daro has a planned layout with rectilinear buildings arranged on a grid plan . Most were built of fired and mortared brick; some incorporated sun - dried mud - brick and wooden superstructures . The covered area of Mohenjo - daro is estimated at 300 hectares . The Oxford Handbook of Cities in World History offers a "weak" estimate of a peak population of around 40,000 . </P> <P> The sheer size of the city, and its provision of public buildings and facilities, suggests a high level of social organization . The city is divided into two parts, the so - called Citadel and the Lower City . The Citadel--a mud - brick mound around 12 metres (39 ft) high--is known to have supported public baths, a large residential structure designed to house about 5,000 citizens, and two large assembly halls . The city had a central marketplace, with a large central well . Individual households or groups of households obtained their water from smaller wells . Waste water was channeled to covered drains that lined the major streets . Some houses, presumably those of more prestigious inhabitants, include rooms that appear to have been set aside for bathing, and one building had an underground furnace (known as a hypocaust), possibly for heated bathing . Most houses had inner courtyards, with doors that opened onto side - lanes . Some buildings had two stories . </P> <P> In 1950, Sir Mortimer Wheeler identified one large building in Mohenjo - daro as a "Great Granary". Certain wall - divisions in its massive wooden superstructure appeared to be grain storage - bays, complete with air - ducts to dry the grain . According to Wheeler, carts would have brought grain from the countryside and unloaded them directly into the bays . However, Jonathan Mark Kenoyer noted the complete lack of evidence for grain at the "granary", which, he argued, might therefore be better termed a "Great Hall" of uncertain function . Close to the "Great Granary" is a large and elaborate public bath, sometimes called the Great Bath . From a colonnaded courtyard, steps lead down to the brick - built pool, which was waterproofed by a lining of bitumen . The pool measures 12 metres (39 ft) long, 7 metres (23 ft) wide and 2.4 metres (7.9 ft) deep . It may have been used for religious purification . Other large buildings include a "Pillared Hall", thought to be an assembly hall of some kind, and the so - called "College Hall", a complex of buildings comprising 78 rooms, thought to have been a priestly residence . </P> <P> Mohenjo - daro had no series of city walls, but was fortified with guard towers to the west of the main settlement, and defensive fortifications to the south . Considering these fortifications and the structure of other major Indus valley cities like Harappa, it is postulated that Mohenjo - daro was an administrative center . Both Harappa and Mohenjo - daro share relatively the same architectural layout, and were generally not heavily fortified like other Indus Valley sites . It is obvious from the identical city layouts of all Indus sites that there was some kind of political or administrative centrality, but the extent and functioning of an administrative center remains unclear . </P>

In which city of harappan civilization was the great granary excavated