Jantar Mantar, one of the several observatories raised by Maharaja Jai Singh II of jaipur, is a unique structure raised in 1724 in the heart of Delhi's comercioal centre near Connaught place. The various abstract structures within are, in fact, instruments that were used for keeping track of celestial bodies. The monument is dominat3ed by a huge sundial known as Samrat Yantra or 'Prince of Dials', meant to measure acurate time of the day. The two pillars on the south west of Mishra Yantra are meant to dermine the shortest and longest days of the year. Interestingly, in December one pillar completely covers the other with its shadow while in June it does not cast any such shadow at all.

After completion of the first Jantar Mantar and with a view to verifying astronomical observations made at Delhi, Jai Singh built similar observatories at other important cities like Jaipur, Varanasi, Ujjain and Mathura. ai Singh himself was a noted scholar of mathematics and astronomy.