I went to India for the first time in 2001 and went back 10 years later. Both times, I went to Varanasi.
There is something special about this city dedicated to the god Shiva. Built on the banks of the sacred Ganges, people travel kilometers to purify and chase away their sins into the river, as the last step before salvation. It is amazing to see this, knowing that the Ganges is the most polluted river in the world. Yet, feeling the spirituality of both life and death makes you want to wander days and days in the streets of Varanasi.
After visiting India, I felt I could go just about anywhere.