Jantar Mantar Jaipur

Jantar Mantar is an open-air observatory built by Maharaja Sawai Jai Singh II, the founder of Jaipur and a keen student of astronomy. The site next to City Palace was completed in 1734, with work on the instruments continuing for a few more years. Jai Singh built several observatories in northern India, and this is the largest and best preserved. It was inscribed as a UNESCO World Heritage Site in 2010.

The site holds 19 instruments made mostly of stone and masonry, designed to measure time, track the positions of stars and planets, and predict eclipses. Their sheer scale was the point: the larger the instrument, the finer the readings. The most striking is the Vrihat Samrat Yantra, a huge sundial whose triangular gnomon rises about 27 m, its slope set at 27 degrees to match Jaipur's latitude. Its shadow moves across the curved scale fast enough to see, at about a millimetre a second.

Other instruments worth looking out for include the Jai Prakash, a pair of sunken hemispherical bowls mapping the sky; the Rama Yantra, cylindrical structures for measuring altitude and azimuth; the Rashi Valaya, a group of twelve instruments, one for each sign of the zodiac; and the Yantra Raj, a large bronze astrolabe. The Dhruva Darshak Pattika was used to locate the pole star.

Without explanation, the site can look like an abstract sculpture garden, so a guide is genuinely useful here. Allow around an hour. There is very little shade, so come early or late in the day and bring a hat and water in the warmer months. The ground is mostly flat, which makes it one of the easier Jaipur sights for families and visitors who prefer to avoid steep climbs. Children often enjoy watching the sundial shadow move.

Jai Singh built five observatories in total, and the Jaipur one is the largest. An interpretation centre on site helps explain how the instruments were used before you go out among them.

Jantar Mantar is directly beside City Palace and a short walk from Hawa Mahal, and the three make a natural half-day route through the old city. Johari Bazaar and the other old city bazaars are close by for lunch and shopping afterwards.