Jantar Mantar is a 18th century (1727-1734) large-scale Architectural Observatory in India designed and built by Maharaja Jai Singh II, the founder of Jaipur, Rajasthan, India. (There were five Jantar Mantars built in India, but only four remain.) The largest and best preserved Jantar Mantar is in Jaipur. One of the world's largest sundials is at Jantar Mantar, Jaipur along with a collection of 19 large astronomical instruments to observe the Universe, cosmos, stars, constellations, eclipses and more.