At Jantar Mantar, the visitor gets a glimpse of the scientific temperament of Sawai Jai Singh. With his passion for astronomical studies, he studied the work of Hindu, Islamic and Western scholars. The astronomical instruments here, built in stone and marble with guidance from by Pandit Jaganath, Kewal Ram and Vidhyadhar Bhattacharaya, are accurate to a remarkable degree.

The most striking instrument at Jantar Mantar is the Brihat Samarat Yantra sundial, an imposing edifice to the far left of the observatory complex. The shadow it casts moves up to four metres each hour. It also aids in the calculation of local and meridian pass time, and various attributes of heavenly bodies, including their declination and altitude. The Jai Prakash Yantra measures the rotation of the Sun and also can be used to find out its longitude and latitude.

The movement of stars can be traced with remarkable accuracy with the Ram Yantra. Calculations based on the Hindu calendar, festivals and other religious times are also made with the help of this instrument.