Jantar Mantar New Delhi, Feb 2011; ("the instrument and Formula") built in 1710 by Maharaja Sawai Jai Singh is an astronomical observatory and well worth the visit. You can stop at the renovated and lovely old Imperial Hotel http://www.theimperialindia.com/ for a drink and lunch out in the garden area, it's then only a short walk to Jantar Mantar.
There is a similar site in Jaipur.Patio area at the lovely old Imperial Hotel http://www.theimperialindia.com/ only a short walk to Jantar Mantar.
For a special tour of Delhi! Hotel car at Imperial Hotel http://www.theimperialindia.com/ only a short walk to Jantar Mantar.
http://www.cottageyesplease.com/ in Pahar Ganj. Stayed here fwith Keith, John and Wm for two nights in Feb 2011, basic, but comfortable, friendly and helpful staff and a good shower. There are also decent restaurants right across the street for breakfast etc