The Jantar Mantar at Delhi, is one of several astronomical observatories raised by Maharaja Jai Singh II of Jaipur, in 1724. The various abstract structures within the Jantar Mantar are, in fact, instruments that were used for keeping track of celestial bodies. Yet, Jantar Mantar is not only a timekeeper of celestial bodies, it also tells a lot about the technological achievements under the Rajput kings and their attempt to resolve the mysteries regarding astronomy. The Jantar Mantar of Delhi is only one of the five observatories built by Sawai Jai Singh II, the other four being located at Jaipur, Varanasi, Ujjain and Mathura. Jai Singh named his observatory Jantar Mantar, which is actually pronounced, as ‘Yantra Mantra’, yantra for instrument and mantra for formula. A huge sundial known as ‘Samrat Yantra’ or ‘Prince of Dials’, meant to measure accurate time of the day within half a second and the declination of the sun and other heavenly bodies dominates it. Jai Singh himself designed this yantra. Other yantras were also meant for the study of heavenly bodies, plotting their course and predicting eclipses. The Jantar Mantars may have fallen into disuse but they remain an integral part of India’s scientific heritage. It presents that the spirit of scientific enquiry was not dead in India and would have yielded rich results if only an opportunity of research and development had been given to it.