Jaipur, Rajasthan 302002, India
Jantar Mantar is the world's largest sundial. In 1728, Sawai Jai Singh II, rajah of Jaipur, dispatched his emissaries across the globe to gather the most accurate astronomical data possible. When they returned, Jai Singh ordered the construction of the Jantar Mantar complex in New Delhi, a monumental astronomical observatory constructed entirely out of stone and based on the astronomical tables of the French mathematician Phillipe de la Hire. In all Sawai Jai Singh built a total of five observatories, with the largest in his hometown of Jaipur.