Jantar Mantar is very popular among tourists and the people of Delhi. The structure is another great masterpiece of Indian architecture which shows the scientific acumen of ancient India. Jantar Manter is situated at Parliament Street, very close to Connaught Place. Jantar Mantar is also called Delhi Observatory. It is maintained by the Jaipur government because it was built by Maharaja Sawai Jai Singh II of Jaipur in 1710 A.D.

A unique structure raised in 1724, now lies in the heart of Delhi's commercial centre near Connaught place. This is the Jantar Mantar, one of several astronomical observatories raised by Maharaja Jai Singh II of Jaipur. 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.

All of these were built as far back as AD 1724-1730 during the period generally known as the dark age of Indian history, when the last great Mughal emperor Aurangzeb had died and the Mughal Empire was rapidly declining. During this period of turmoil, Muhammad Shah ascended the throne of the Mughal Empire. As many enemies surrounded him, he sought the alliance of the Hindu rulers. Of these, the most notable was Sawai Jai Singh II of Amber, who came into limelight since the days of Aurangzeb. When Jai Singh ascended the throne of Amber in 1699, he was barely eleven, but sharp and shrewd far beyond his years. The then Mughal emperor Aurangzeb was so impressed with the young ruler that he gave Jai Singh II the title of 'Sawai', meaning one and a quarter of an average man in worth.

It is a remarkable structure which consists of fourteen geometric devices used for measuring time, forecasting weather changes, predicting behaviour of planets and finding extraterrestrial altitude. All these devices are fixed structures and point to a specific direction. The largest device or instrument is the Samrat Jantar which is 90 feet high and its shadow is plotted in such a manner so that is shows the exact time of the day. Any weather change or the onset of monsoons can be ascertained by the Hindu Chhatri, which is a small domed structure.