Jantar Mantar is a planet observatory at Jaipur that was constructed by Maharaja Sawai Jai Singh. The king was very much interested in astrology and he constructed this planet observatory to observe the planets in a more scientific manner and enhance his knowledge. The place has many astronomical instruments. Brass and stone are the two major materials used in the construction of these instruments. These instruments help in knowing about the precise astronomical positions of various heavenly bodies. The place is also famous for the largest sundial of the world, Samrat Yantra. This UNESCO World Heritage Site was built in 1738.