The Jantar Mantar Observatory was built by Maharaja Sawai Jai Singh II, as a focal point of his new capital, Jaipur, the first and earliest geometrically planned city in India. Jantar Mantar is the most complete and best-preserved great observatory site built in the Ptolemaic tradition. This tradition developed from Classical Antiquity through to medieval times and from the Islamic period through to Persia and China. Jantar Mantar was greatly influenced by earlier great observatories inside central Asia, Persia and China.

Designed for the observation of astronomical positions with the naked eye, they embody several architectural and instrumental innovations. The site shows important architectural and instrumental innovations and the size of some of the instruments is among the largest in the world. There are instruments working in each of the three main classical coordinate systems: the horizon-zenith local system, the equatorial system and the ecliptic system. One instrument (Kapala Yantra) is able to work in two systems and to transform coordinates directly from one system to the other. This is one of the most complete and impressive collections in the world of pre-telescopic masonry instruments in functioning condition.

This is the most significant, most comprehensive, and the best preserved of India’s historic observatories. It is an expression of the astronomical skills and cosmological concepts of the court of a scholarly prince at the end of the Mughal period.

Outstanding Universal Value 

The Jantar Mantar, Jaipur, is an astronomical observation site built in the early 18th century. It includes a set of some twenty main fixed instruments. They are monumental examples in masonry of known instruments but which in many cases have specific characteristics of their own. The Jantar Mantar is an expression of the astronomical skills and cosmological concepts of the court of a scholarly prince at the end of the Mughal period.

The Jantar Mantar observatory in Jaipur constitutes the most significant and best preserved set of fixed monumental instruments built in India in the first half of the 18th century; some of them are the largest ever built in their categories. Designed for the observation of astronomical positions with the naked eye, they embody several architectural and instrumental innovations. The observatory forms part of a tradition of Ptolemaic positional astronomy which was shared by many civilizations. It contributed by this type of observation to the completion of the astronomical tables of Zij. It is a late and ultimate monumental culmination of this tradition.

Through the impetus of its creator, the prince Jai Singh II, the observatory was a meeting point for different scientific cultures, and gave rise to widespread social practices linked to cosmology. It was also a symbol of royal authority, through its urban dimensions, its control of time, and its rational and astrological forecasting capacities. The observatory is the monumental embodiment of the coming together of needs which were at the same time political, scientific, and religious.

Criterion (iii): The Jantar Mantar in Jaipur is an outstanding example of the coming together of observation of the universe, society and beliefs. It provides an outstanding testimony of the ultimate culmination of the scientific and technical conceptions of the great observatory devised in the medieval world. It bears witness to very ancient cosmological, astronomical and scientific traditions shared by a major set of Western, Middle Eastern, Asian and African religions, over a period of more than fifteen centuries.

Criterion (iv): The Jantar Mantar in Jaipur is an outstanding example of a very comprehensive set of astronomical instruments, in the heart of a royal capital at the end of the Mughal period in India. Several instruments are impressive in their dimensions, and some are the largest ever built in their category.

Source:

http://whc.unesco.org/en/list/1338

https://www3.astronomicalheritage.net/index.php/show-entity?idunescowhc=1338