The Harappan Civilization

1. Harappa: Discovered in 1921 by Rai Bahadur Daya Ram Sahni on the left bank of the River Ravi (in Montgomery district, Punjab, Pakistan).
   2. Mohenjo-daro: Discovered in 1922 by Rakhaldas Banerjee on the right bank of the River Indus (in Larkana district, Sindh, Pakistan).

• Structure: A rectangular swimming basin measuring $11.88\text{ m} \times 7.01\text{ m}$ with a depth of $2.43\text{ m}$. Two flights of brick steps descend into it from the north and south. It is built of precision baked bricks set in gypsum mortar, sealed with a $3\text{ cm}$ thick layer of natural bitumen (asphalt) for complete waterproofing. Surrounded by pillared verandahs and dressing rooms supplied by a freshwater well, with a corbelled culvert for draining dirty water.
• Significance: It was not a private bath, but a sacred public structure used for ritualistic religious purification ablutions during important festivals, resembling temple tanks in modern India.

1. House-to-Street Connection: Every house had a paved bathroom connected to street drains via clay pipes embedded through exterior walls.
   2. Covered Channels: Street drains ran alongside major roads and were covered with flat brick tiles or dressed limestone slabs that could be easily lifted for municipal cleaning.
   3. Manholes and Soak Pits: Drains were fitted with inspection manholes and deep soak pits at regular intervals where heavy solid waste settled, allowing only clean liquid effluent to flow into main outfall channels outside the city.

• The Citadel: An elevated, fortified acropolis constructed in the western section of the city, raised on a massive artificial platform of mud-bricks.
• Purpose: It housed the ruling administrative authorities and vital public buildings—such as the Great Bath, the Great Granary, the pillared assembly hall, and the administrative offices—protecting them from periodic river floods and potential unrest.

• Description: A famous $10.5\text{ cm}$ high statuette found at Mohenjo-daro depicting a slender young girl standing in a confident, natural posture with one hand on her hip and head tilted back, her left arm covered almost entirely in bangles.
• Significance: Cast in bronze using the advanced Lost-Wax Technique (cire-perdue), it proves that Harappan artisans had mastered sophisticated metallurgy, alloy casting, and anatomical realism.

• Lothal Dockyard: A massive tidal basin built of kiln-burnt bricks connected by a sluice gate to the Bhogavo/Sabarmati river and the Gulf of Khambhat.
• Significance: It is the world's earliest known engineered tidal dockyard. It proves that the Harappans were an active maritime trading civilization that navigated the Arabian Sea to trade with Mesopotamia, Oman, and the Persian Gulf.

• Description: A steatite seal depicting a three-faced male deity sitting cross-legged in a yogic posture (padmasana) wearing a horned headdress. He is surrounded by four wild animals: an elephant, a tiger, a rhinoceros, and a buffalo, with two deer sitting beneath his stool.
• Religious Significance: Sir John Marshall identified this figure as "Proto-Shiva" (an early representation of Lord Shiva as Pashupati—the Lord of Beasts, and Mahayogi). It proves that Shiva worship dates back to Harappan times.

1. Ecological Changes & Desertification: Deforestation (for baking millions of bricks) reduced rainfall, leading to drought and expansion of the Thar desert.
   2. Shifting Course of Rivers: Tectonic movements caused the Indus River to change its course or caused the drying up of the sacred Saraswati (Ghaggar-Hakra) river.
   3. Catastrophic Floods: Recurring catastrophic flooding of the Indus submerged cities under deep alluvial silt.
   4. Aryan Invasion Hypothesis: Proposed by Mortimer Wheeler based on skeletons found in streets of Mohenjo-daro and Rigvedic references to Indra destroying fortified cities (Purandara).