The site is a collection of 19 astronomical instruments built by the Rajput king Sawai Jai Singh II, the founder of Jaipur. It features the world's largest stone sundial, and is a UNESCO World Heritage site. The instruments allow the observation of astronomical positions with the naked eye. The observatory is an example of the Ptolemaic positional astronomy which was shared by many civilizations. The monument features instruments operating in each of the three main classical celestial coordinate systems: the horizon-zenith local system, the equatorial system, and the ecliptic system.