English: The Jantar Mantar is an architectural ephemeris, built by Maharaja (King) Jai Singh II at his then new capital of Jaipur between 1727 and 1734. It is modeled after the one that he had built for him at the Mughal capital of Delhi. The Jaipur observatory is the largest and best preserved of these of the five observatories he had built. The World Heritage List describes it as "an expression of the astronomical skills and cosmological concepts of the court of a scholarly prince at the end of the Mughal period". Early restoration work was undertaken under the supervision of Major Arthur Garrett, a keen amateur astronomer, during his appointment as Assistant State Engineer for the Jaipur District. Jantar means "instrument" and Mantar means "calculation" and were used by the Jyotish astrologers to measure the placement of the Sun, Moon and planets.