Jantar Mantar is a astronomical observation site, built in 18th century, located in Jaipur city at Rajasthan, India. It is collection of architectural astronomical instruments. It is a inscribed in World Heritage List as "an expression of astronomical skills and cosmological concepts". It was built by Jaipur Maharaja Jai Singh-II between AD 1727 and 1734. Its name Jantar Mantar is a hindi language word which means calculation instrument. "Jantar" means instrument and "Mantar" means formula and collectively means instrument based on some calculation formula.
From AD 1727 to 1734, Jaipur Maharaja Jai Singh-II constructed 5 astronomical observations in west-central India, including Delhi and Jaipur. Jantar Mantar at Jaipur constitutes the most significant and well preserved set of fixed monumental instruments built in India. Jaipur's Jantar Mantar observatory consists of 14 major geometric devices used for measuring time, predicting eclipses. It is also used for tracking star's location as the earth orbits around the sun, ascertaining the declinations of planets and determining the celestial altitudes and related ephemerides. It has embodied several architectural and instrumental innovations that enables observation of astronomical positions with the naked eye