Southeast of the City Palace, the fascinating Jantar Mantar (tourism.rajasthan.gov.in/jantar-mantar.html; adult/student ₹202/102, composite ticket ₹1102/552) was constructed in 1728 as an astronomical observatory, on the orders of the scientifically curious Jai Singh II. Kids and anyone with a scientific leaning will love investigating this collection of curious objects, used to measure the movements of celestial bodies.
The name comes from Sanskrit yantra mantrana, meaning "instrument of calculation." Stairs to nowhere climb over calibrated crescents, dangling disks and rings form giant astrolabes, and marble-lined basins allow precise calculations of the movements of the spheres. The Laghu Samrat Yantra – a supersized sundial – can measure the time accurately to within 20 seconds (you can test it, provided the sun is shining).
Elsewhere, small structures track the constellations of the zodiac, while the enormous Samrat Yantra soars skywards, measuring the movement of the sun. A guide (from ₹400) is highly recommended if you want to learn how each fascinating instrument works, or read up on the instruments at jantarmantar.org. The site is best explored on a composite two-day ticket.
