Jantar Mantar
A Jantar Mantar (जंतर मंतर, Hindustani pronunciation: [d͡ʒən̪t̪ər mən̪t̪ər] ‘calculation instruments’) is an assembly of stone-built astronomical instruments, designed to be used with the naked eye. There were five Jantar Mantars in India, built between 1724 and 1735.