Before the giant Jantar Mantars were built, the kingdom official stargazers would use smaller, often handheld instruments to study the skies. However, they often had arguments about whose measurements were correct. Maharaja Jai Singh ll built the giant Jantar Martars because he believed that if the instruments were much bigger and carefully fixed in position, people could take better measurements. The Jantar Mantar at Jaipur is considered one of the Maharaja's greatest achieve nments.