Jantar Mantar

Lonely Planet review

Near the City Palace is Jantar Mantar, an observatory begun by Maharaja Jai Singh II (1693-1743) in 1728, which at first glance looks like a collection of mammoth, bizarre sculptures. If sensing you've stepped into Alice Through the Looking Glass is not enough, the Rs 150 guided tour (30 minutes to one hour) is worthwhile.

Guides provide fascinating explanations of how each of the instruments work, and how through watching, recording and meticulous calculation, Jai Singh measured time by place the sun's shadow fell on the huge sundials and charted the annual progress through the zodiac. Each construction has a specific purpose, such as calculating eclipses. The most striking instrument is the sundial, with its 27m-high gnomon; the shadow this casts moves up to 4m per hour.

Before constructing the observatory, Jai Singh sent scholars abroad to study foreign constructs. He built five in total, and this is the largest and best preserved (it was restored in 1901). Others are in Delhi, Varanasi and Ujjain. The fifth, the Muttra observatory, is gone.