Jantar Mantar observatory was built by the ruler of Jaisingh in Varanasi in line with those built in Delhi, Mathura, Ujjain and Jaipur observatories. The Varanasi observatory has all the instruments which were required to record the motion, speed and properties of various stars and planets and other cosmic objects. The observatory was built in 1600 and still the instruments give the exact measurements which can match any modern instrument.