The Bronze Age in the Indian subcontinent began around 3300 BCE. Along with Ancient Egypt and Mesopotamia, the Indus valley region was one of three early cradles of the civilization of the Old World. Of the three, the Indus Valley Civilization was the most expansive, and at its peak, may have had a population of over five million. The civilization was primarily centered in modern-day Pakistan, in the Indus river basin, and secondarily in the Ghaggar-Hakra river basin in eastern Pakistan and northwestern India. The Mature Indus civilization flourished from about 2600 to 1900 BCE, marking the beginning of urban civilization on the Indian subcontinent. The civilization included cities such as Harappa, Ganeriwala, and Mohenjo-daro in modern-day Pakistan, and Dholavira, Kalibangan, Rakhigarhi, and Lothal in modern-day India. Inhabitants of the ancient Indus river valley, the Harappans, developed new techniques in metallurgy and handicraft (carneol products, seal carving), and produced copper, bronze, lead, and tin. The civilization is noted for its cities built of brick, roadside drainage system, and multi-storeyed houses and is thought to have had some kind of municipal organization. After the collapse of the Indus Valley civilization, the inhabitants of the Indus Valley civilization migrated from the river valleys of Indus and Ghaggar-Hakra, towards the Himalayan foothills of the Ganga-Yamuna basin.