The jantar Mantar is in heart of modern city of New Delhi. Very close to CP and Rajiv Chock Metro Station. The site is one of five built by Maharaja Jai Singh ll of jaipur, from 1723 onwords, as he was given by Mughal emperor Muhammad Shah the task of revising the calendar and astronomical tables. It consists of 13 architectural astronomy instruments.
The primary purpose of the observatory was to compile astronomical tables, and to predict the times and movements of the sun, moon and planets. Some of these purposes nowadays would be classified as astronomy
Jantar Mantar of delhi was Completed in 1724.