The Jantar Mantar is an impressive collection of architectural astronomical instruments located in India, built by the Rajput king Sawai Jai Singh II. This remarkable observatory, completed in 1734, is home to the world's largest stone sundial, the Vrihat Samrat Yantra, and has been designated as a UNESCO World Heritage Site. Designed for the observation of astronomical positions with the naked eye, the Jantar Mantar reflects the advanced scientific knowledge and cosmological concepts of its time. It stands as a testament to the ingenuity and foresight of Sawai Jai Singh II, whose passion for astronomy and architecture combined to create this historic site.