I was about to suggest Varanasi and just noticed it's in your OP. I went there on my first visit to India years ago (as a backpacking holidaymaker) and really enjoyed it.
Originally Posted by GUWonder
I also suggest Agra and Fatehpur Sikri. Could be done in 1.5 days.
I second Fatehpur Sikri. I went there almost by mistake on the same first visit and was very impressed by it. GUWonder will no doubt correct me if I'm wrong
but IIRC, the mosque there is apparently a copy of one of the major mosques in Mecca.