The Jantar Mantar is an astronomical observatory with masonry instruments, built in 1724 by Sawai Jai Singh II, the mathematician and astronomer king of Amber. The Jantar Mantar in Delhi was one of five such instruments built in Jaipur, Ujjain, Mathura and Varanasi.

The Amber King was a keen scholar of astronomy. He studied the movement of the heavenly as a reputed astronomer in line with Ulugh Beg, Tycho Brahe and John Flamstead. The Maharaja found the existing astronomicalinstruments to record totally accurate observations and so he decided that bigger structures should be constructed. The instruments at Jantar Mantar are fascinating for their novel approach.

The Samrat or Yantra supreme – the largest structure shaped like a right-angled triangle, is actually a huge sun-dial; the other fiveinstruments are intended to show the movements of the sun, moon, etc. According to the rays of the Sun falling on it, it helped the people calculate to some extent the time of the day.