How did the geography of the Indian subcontinent influence the development of civilization there?

The Indian subcontinent consists of present-day India, Pakistan, Bhutan, Nepal, and Bangladesh. The northern part of this subcontinent is bordered by the rugged Himalayas, so that land is only accessible via passes. The Himalayas were a vital source of security to early civilizations in the region as they provided a kind of mighty wall that protected these people from foreign invasion. Also, these mountain ranges have contributed to suitable climatic conditions in the region as they retain the moisture-laden southwest monsoon winds that cause rain and block the very cold winds that blow from central parts of Asia. The monsoon winds encouraged trade by sea.
At the foot of the mountain ranges lie vast fertile soils deposited by overflows from rivers such as the Indus, Ganges, and Brahmaputra that come from the Himalayan ranges. These areas have attracted lots of agricultural activity over the years. The rivers themselves have helped in farming, transportation, and trade. In fact, the Indus valley civilization developed around the Indus River at about 2500–1700 BCE and grew majorly by farming crops such as wheat, sesame, mustard, melons, and so on. These people also kept animals such as cattle, fowl, pigs, and buffalos.
https://www.britannica.com/topic/Indus-civilization