Where is the world’s largest stone sundial?

The Jantar Mantar monument in Jaipur, Rajasthan is a collection of nineteen architectural astronomical instruments, built by the Rajput king Sawai Jai Singh II, and completed in 1734. It features the world’s largest stone sundial, and is a UNESCO World Heritage site.

The name is derived from jantar, yantra in Sanskrit: यन्त्र, meaning instrument, machine, and mantar, from mantrana in Sanskrit meaning, to calculate. Therefore Jantar Mantar literally means calculating instrument.

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.

Jantar Mantar is managed under the Archeological Sites and Monuments Act of Rajasthan since 1961, and protected as a National Monument of Rajasthan since 1968.

The Vedas mention astronomical terms, measurement of time and calendar, but do not mention any astronomical instruments. The earliest discussion of astronomical instruments, gnomon and clepsydra, is found in the Vedangas, ancient Sanskrit texts. The gnomon (Shanku) found at Jantar Mantar is discussed in these 1st millennium BCE texts and in many later texts such as the Katyayana sulbasutras. Other discussions of astronomical instruments are found in Hindu texts such as the 4th century BCE Arthashastra, Buddhist texts such as Sardulakarna-avadana, and Jain texts such as Surya-prajnapti.

The theories behind the instruments are found in texts by ancient authors of the 5th century BCE - Aryabhatta, 6th century BCE - Brahmagupta and Varahamihira, 9th century BCE - Lalla, 11th century BCE - Sripati and Bhaskara. The texts of Bhaskara have even dedicated chapters on instruments and he calls them Yantra-adhyaya.

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What kind of astronomy does this observatory feature?

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