Indian girl climbing stairs at the Jantar Mantar astronomical observatory. Jaipur City, Rajasthan State, India. Between 1727 and 1734 Maharajah Jai Singh II of Jaipur City in the State of Rajasthan India constructed five astronomical observatories in west central India. The observatories, or "Jantar Mantars", incorporate unique buildings with combinations of geometric forms with a specialized function for astronomical measurement.