Jantar Mantar in New Delhi is a surprisingly amazing place that holds a historical significance. The Observatory was also built by the talented Maharaja Jai Singh II. He is said to be an avid astronomy enthusiast and built observatories in Jaipur, Delhi and Varanasi. With five observatories, the Jantar Mantar Observatory is the largest and most preserved. The materials used in the building are ancient sedimentary rock, but one can't see how old they are because they look very modern. The world's largest sundial, two time measuring instruments with a large circle, 12 constellation triangle building for the layman seems so amazing, must be the best place for astronomy enthusiasts!