Three things to do when in Calcutta as I like to call it:
1. Go shopping- make the most of the street markets and don't forget to bargain.
2. Eat street food- Pau Bhaji, Jhal Moori some items that are absolutely delish. But remember if you can't take the heat, maybe ask them to make it less spicy.
3. Watch a Bollywood film- when in India! An absolute must do.