Immediately south of the City Palace lies the remarkable Jantar Mantar, a large grassy enclosure containing eighteen huge stone astronomical measuring devices constructed between 1728 and 1734 at the behest of Jai Singh, who invented many of them himself, their strange, abstract shapes lending the whole place the look of a weird futuristic sculpture park. The Jantar Mantar is one of five identically named observatories created by the star-crazed Jai Singh across North India, though his motivation was astrological rather than astronomical.
It’s a good idea to pay for the services of a guide to explain the workings of the observatory, which was able to identify the position and movement of stars and planets, tell the time and even predict the intensity of the monsoon. Probably the most impressive of the observatory’s constructions is the 27-metre-high sundial, the Samrat Yantra, which can calculate the time to within two seconds. A more original device, the Jaiprakash Yantra, consists of two hemispheres laid in the ground, each composed of six curving marble slabs with a suspended ring in the centre, whose shadow marks the day, time and zodiac symbol – vital for calculating auspicious days for marriage.