Jantar Mantar, in Jaipur, India, is a fantasy land of science and architecture. Built in the 1700s, it houses about 20 astronomical instruments: beautiful arches, domes, and spires designed to plot the motions of the Sun and other objects.

The observatory was founded by Maharaja Jai Singh II. It was one of five observatories he built across northern India, in the 1720s and ’30s. All of them were known as Jantar Mantar – a name that means “calculating machine.” The Jaipur site was the largest and most important. It’s also the best preserved.

Jantar Mantar’s instruments were all designed to observe the heavens with the eye alone. Several of those were for tracking the motions of the Sun. And some of them were the largest of their kind ever built. One sundial, for example, had a shadow-casting marker almost 75 feet tall. The instruments allowed the site’s 20 or so astronomers to determine the time with an accuracy of just two seconds. They also set the calendar.

Other instruments tracked the positions of the stars and planets. That includes a set of a dozen identical instruments, each of which aligned to one of the constellations of the zodiac. That provided important observations for court astrologers.

The site was in steady use until about 1800, and intermittent use after that. It underwent several upgrades and restorations. Today, it’s a World Heritage site – an astronomical fantasy land.

Script by Damond Benningfield