The jantar mantar is located in the modern city of New Delhi. It consists architectural astronomy instruments.
The site is one of five built by jay singh, from 1724 onwards, as he
was given by mugal king the task of revising the calendar and
astronomical tables. There is a plaque fixed on one of the structure
jantar mantar observatory in delhi that
was placed there in 1910 mistakenly dating the construction of the
complex to the year 1710. Later research, though, suggests 1724 as the
actual year of construction.
The primary purpose of the observatory was to compile astronomical
tables, and to predict the times and movements of the sun, moon and
planets. Some of these purposes nowadays would be classified as astronomy.