Jantar Mantar

What you see aren't modern sculptures but astronomical instruments of stone and brick. They were built for Maharaja Sawai Jai Singh II of Amber, the founder of Jaipur, a man passionate about mathematics and astronomy.

1An observatory without telescopes

Jai Singh wanted to correct the calendars and astronomical tables of his day, which were full of errors. His idea was that a huge instrument gives more precise readings than a small one. He built five observatories in northern India: Delhi, Jaipur, Ujjain, Varanasi and Mathura. Delhi's was the first. A plaque put up in 1910 says it dates from 1710, but later research places it around 1724.

2The instruments

The largest is the Samrat Yantra, the "supreme instrument". It's a giant triangular sundial whose shadow marks the time on two curved quadrants. Beside it, the Jai Prakash consists of two hemispherical bowls for locating the stars. The Ram Yantra is made of open cylinders and was used to measure the altitude of celestial bodies. The Misra Yantra, the "mixed instrument", combines several functions.

Jai Singh watched the sky like a scientist and built like an emperor.

Today the street beside the observatory is also Delhi's official protest site, close to Parliament.

3What to look for

• The great triangle of the Samrat Yantra and its staircase.
• The bowls of the Jai Prakash.
• The Misra Yantra, with its silhouette of red arches.