The scholarly Sawai Jai Singh II was well aware of European developments in the field of astronomy and wanted to create one of the world's finest observatories. He supervised the design and construction of five remarkable facilities in northern India, of which this is the largest and best preserved. Built in 1726 out of masonry, marble, and brass, it's neatly laid out and equipped with simple solar instruments called yantras, which look like large, abstract sculptures, and are remarkably precise in measuring complex celestial data like time, the location of stars, angles of planets, and predicting forthcoming eclipses. Such accuracy was desired for creating astrological predictions. If you don't have a guide with you, try to recruit one to explain how these devices work, as they're fascinating and, for nonscientists, somewhat complicated. Avoid the observatory at noon, as it can be very hot.
Tripoliya Bazaar, near entrance to City Palace, Jaipur, Rajasthan, 302001, India