The Jantar Mantar is a collection of architectural astronomical instruments; built by Maharaja Sawai Jai Singh who was a Rajput king. The observatory consists of fourteen major geometric devices for measuring time; predicting eclipses; tracking stars' location as the earth orbits around the sun; ascertaining the declinations of planets; and determining the celestial altitudes and related ephemerides.

Jaipur is the capital and largest city of the Indian state of Rajasthan. It was founded on 18 November 1727 by Maharaja Sawai Jai Singh II; the ruler of Amber; after whom the city was named. The city today has a population of 3.1 million. Jaipur is known as the Pink City of India.

The city is remarkable among pre-modern Indian cities for the width and regularity of its streets which are laid out into six sectors separated by broad streets 34 m (111 ft) wide. The urban quarters are further divided by networks of gridded streets. Five quarters wrap around the east; south; and west sides of a central palace quarter; with a sixth quarter immediately to the east. The Palace quarter encloses the sprawling Hawa Mahal palace complex; formal gardens; and a small lake. Nahargarh Fort; which was the residence of the King Sawai Jai Singh II; crowns the hill in the northwest corner of the old city. The observatory; Jantar Mantar; is a World Heritage Site. Pictures From Asia David Henley