The first place I went was Delhi Haat. They have more than 15 food stalls, each representing cuisine from India's various states. I had papadums and parathas stuffed with paneer (cheese), plus raita and various sauces. Amazing!
The most unexpected thing I ate was spicy tapioca. There was a lot of lime-leaf involved, so this had a great citrusy flavor.
I also indulged my love of street food at Central Market in Lajpat Nagar. Lentil fritters with grated radish and a green herb I couldn't identify, and chole (spicy chickpeas) and fry bread.
The best and least photogenic meal (sorry, no picture) was at Karim's. They have a number of locations, but the one near Chandni Chowk had great atmosphere. The butter chicken was heavenly, and the biryani was spectacular. If you're in Delhi, Karim's is not to be missed.
I visited the spice market in Chandni Chowk and got up close and personal with with elements behind the amazing flavors in Indian cuisine, including nutmeg flowers, which I'd never seen before.
I'm bringing a number of different spices home, and hoping to recreate some of these meals.