Jantar Mantar of Jaipur is one of the five observatories constructed by Jai Singh II. Ujjain, Delhi and Varanasi are the other cities that house the remaining Jantar Mantars but there remain no traces of the one at Mathura.

Among the many instruments that are part of this observatory is the world’s biggest sundial. Jantar Mantar is located just a stone’s throw from City Palace and Hawa Mahal and features instruments made of stone and brass that were built using instrument design principles from ancient texts.

In all there are 19 instruments that help observe astronomical positions with the naked eye. Jantar Mantar is a fine example of Ptolemaic positional astronomy and has instruments that operate in each of the three main classical celestial coordinate systems: the ecliptic system, the horizon-zenith local system and the equatorial system.

When it suffered some damage in the 19th century, Major Arthur Garrett, an amateur astronomer who was posted as the Assistant State Engineer in Jaipur, undertook the first major restoration work on Jantar Mantar. As of 2010, Jantar Mantar has been included in the list of UNESCO World Heritage sites and remains a gem of Jaipur that cannot be missed.