That the community of Mohenjo Daro, which might have included between 20,000 and 40,000 people during the height of its prosperity, was divided into social classes is supported by an examination of the houses in the lower city The scale of the excavations at this site is well illustrated in the work undertaken during the 1926-27 season under the direction of Rai Bahadur Daya Ram Sahni. An area of 150 by 133 meters (495 by 439 ft.) was exposed to a depth of seven meters, incorporating three building phases. As the city plan emerged from the excavation, it became apparent that the area incorporated a main street running on a north-south axis. It extended for at least 300 meters (990 ft.), and various artifacts lay on its surface, including copper amulets, beads, and spear - and arrowheads. To the west lay a series of 66 buildings, divided by narrow lanes in an orderly, but not precise, geometric grid. The houses of the earliest of the three phases were well constructed, with large rooms and high ceilings. One particularly fine building had as many as 35 rooms around a court 19 by 16 meters (62.7 by 52.9 ft.) in extent. It was possible to ascertain the ceiling height as being 3.15 meters (10.3 ft.) in one room by the presence of the holes to take the wooden beams. The walls above this height were part of an upper story. It was found to contain 18 well-cut stone rings with a hole in the middle and two stone plugs with rounded heads that would have fit in the holes in the rings. Their function is unknown, but they may have been lingams and yonis, so familiar in much later Indian and Southeast Asian contexts as representing the male and female genitalia. Two steatite seals were also found in this large house, which must have been occupied by an affluent member of the community.
Immediately to the north, another house lay on the corner of the main street and a narrow lane. A visitor entering the front door from the street would have found herself or himself in a small lobby with a well in one corner. A set of stairs went up to the first floor, and under the stairs there was a small room about one meter square equipped with a drain. This was probably the latrine. A passage divided the rest of the house into two parts and led directly to the bath. Sahni suggested that two living rooms were located on the northern side of the corridor, and a kitchen lay to the south. A seal was found in the debris in the house. By leaving through the front door and turning left into a narrow lane, the occupants could visit a street lined with shops.