Located in the modern city of New Delhi, it consists of 13 architectural astronomy instruments. Built by Maharaja Jai Singh II of Jaipur, it was used for revising the calendar and astronomical tables. The primary purpose of the observatory was to compile astronomical tables, and to predict the times and movements of the sun, moon and other planets. There are four distinct instruments within the observatory and these are Samrat Yantra, the Ram Yantra, the Jayaprakash, and the Mishra Yantra. The observatory is situated in the busy market area of Cannaught palace which is the heart of the city.