There's some incredibly impressive megalithic structures in India. Look up Ajanta and Ellora caves. I believe the Ellora temple is the largest monolithic structure ever created
The Indian region has historically has been pretty resilient to famines, the exception to that is during British rule there were several famines leading to the starvation and deaths of millions. The consensus seems to be that these famines were a result of British policy. I've never heard of this unsustainable growth and famine argument I'd love to read more if you can provide sources
This 1,500-year-old Cave in India was Carved out of a Giant Boulder (lemmy.world)