Jantar Mantar is the largest of the five observatories Jai Singh II built between 1724 and 1735, and the best preserved. Nineteen masonry instruments are set in the open ground beside the City Palace, each built to measure the heavens by eye: the Samrat Yantra, a sundial with a 27-metre gnomon accurate to two seconds; the Jai Prakash, two bowls that map the sky; the Rashivalaya, twelve instruments one for each sign; and the rest.
Jai Singh was a serious astronomer who corrected the tables of his day with these instruments, and the site was inscribed by UNESCO in 2010. The guides explain how each instrument is read; without one, it is a sculpture garden.
What to see
| Name | Where | What it is known for |
|---|---|---|
| Samrat Yantra | Centre | The great sundial; shadow moves six centimetres a minute. |
| Jai Prakash Yantra | South | Two hemispherical bowls mapping the sky. |
| Rashivalaya Yantra | South-east | Twelve zodiac instruments. |
| Ram Yantra | North | Cylindrical instruments for altitude and azimuth. |
| Laghu Samrat | Entrance | The smaller sundial, used to explain the large one. |
Worth knowing
- Take the guide or the audio guide; the instruments mean nothing unread.
- Midday is the time to see the sundial working; the shadow is sharpest.
- Included in the composite ticket.
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