Jantar Mantar

At the ripe age of twelve, the young king Maharaja Sawai Jai Singh II ascended to the throne. Exceptionally curious when it came to the fields of astronomy and mathematics, he would go on to become one of the world’s most ingenious skygazers.

An ardent reader and observer, he caught erroneous calculations about planetary movements from a young age. A desire to correct those while  educating his people about cosmic wonders was among the motivations for the king’s creation of five observatories, commonly known as Jantar Mantars.

Built between 1724 and 1730, they each contain complex, large-scale geometric devices resembling art installations (particularly when being minded by a chromatically synchronized guard). The telescope had been in use for over a century by then, but Jai Singh did not believe that any small device made of brass—whose parts would wear and erode—could deliver precise measurements or an understanding of celestial objects.

Instead, his observatories were built using stone and masonry. Given his capacity to think huge, his “instruments” run as tall as 90 feet high. The Samrat Yantra is a classic example: a sundial that uses a gigantic triangular gnomon (the part that casts a shadow) to track the rate of Earth’s movement.

Four of the five observatories have survived for nearly three centuries. These startling large-scale structures have brought greater precision to India’s celestial measurements while attracting academics, architects, and modern artists—even converting the occasional flat-earther. These installations and the wonder they’ve inspired have secured Jai Singh II’s immortal, astronomical legacy.

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