Jantar Mantar was built by Sawai Jai Singh II in 1725 with the intention of observing the movement of the stars and the planets. This observatory, located at Connaught Place in New Delhi, consists of the salmond colored structures - the Samrat Yantra, the Ram Yantra, the Jai Prakash and the Misra Yantra.
Samrat Yantra, a huge sun dial used to measure the time of the day accurate to within half a second and it was designed by Jai Sing himself. The Ram Yantra and the Jai Prakash are also used for the study of heavenly bodies. For calculating the shortest and the longest days of the year, the two pillars on the south-west of Mishra Yantra was used. In December, one of these pillars covers the other with its shadow. The Ram Yantra determines the position of the sun, moon, planets, stars and other heavenly bodies. For measuring the zodiacal sign or the group of the stars on the meridian, the Jai Prakash was used. Jantar Mantar also known as the Yantra Mandir remains as an integral part of India’s scientific heritage.
Entrance fee is Rs 5 for Indian nationals and US $2 for foreigners.