I already mentioned Tipu's missile tech used against the British.
Other than a birthplace of ideas and religion, the subcontinent also excelled in several fronts, one of which was metallurgy. Swords were an early product and Damascus steel fighting swords used to be sourced from India even before 1000 AD. There was tech available to prevent rusting of steel, now lost to history - which was used to cast a rustproof large Iron pillar around 300 AD. This was without use of using alloys like SS or surface coating like zinc (galvanizing) and the corrosion proofing was endemic and homogenous to the cast iron.
en.wikipedia.org
Of course South Asia formed city centers pretty early, city planning was as advanced as Babylonian and Egyptian civilizations. The excavated city of Mohenjo Daro in Sindh, Pakistan dating 4500 years ago is witness to the high degree of sophistication in city planning, zoning, plumbing and running water. This was more or less universal across the subcontinent, but in areas where there is much water (like in the East and some areas in the South, especially where rivers and deltas exist), the earlier evidence has corroded and de-composed away. But evidence of earlier structures and cities are continually being discovered and excavated. Man builds, nature un-builds.
The weaving tech in the East was exploited early on by the British, but when it competed with their own machine made crude products in the start of the Industrial textile revolution, the British took urgent steps to curb the competition by cutting off Bengal weavers' fingertips.
@Wergeland bhai another thing that Bengal was very good at was large sea-going shipbuilding (wooden ones), from time immemorial. In fact several of the large ships that fought in the Battle of Trafalgar were built in Chittagong. Even today, large local steel-frame river ferries capable of carrying 3000 passengers are welded and built on nothing but temporary stilts and brick foundations and ply on regular overnight routes. The local fleet of passenger river ferries (launches, as they are called locally) will easily exceed seven to eight hundred. This is the oldest transport infra we have extant.
A Note on the Shipbuilding in Bengal in the Late Eighteenth Century - Volume 19 Issue 3
www.cambridge.org
This book seeks to enlighten two grey areas of industrial historiography. Although Bengal industries were globally dominant on the eve of the industrial revolution, no detailed literature is available about their later course of development. A series of questions are involved in it. Did those...
books.google.com
Bangladesh even now is washed and crisscrossed by over 400 rivers, small and large. It used to be 700~800 rivers. some of which have silted and dried up. The large ones (in places) are over 7 KM wide, similar to the Hwang Ho in China. Compared to these, most 'rivers' in other places globally can be considered canals.
en.wikipedia.org