Jantar Mantar observatories were built by Maharaja Jai Singh II of Jaipur in the early 18th century (between 1724-1735). He constructed five observatories in different cities including Delhi, Jaipur, Varanasi, Ujjain, and Mathura to compile astronomical tables. Prithvi Raj, Akbar, and Shah Jahan ruled in different time periods.