The Jaipur Observatory, in northern India. This open-air museum has a collection of astronomical instruments and is officially known as Jantar Mantar, which can be translated as ‘Calculation Instruments’.

It is the biggest stone observatory in the world and is listed as an UNESCO World Heritage Site.

It was built by Maharadja Sawai Jai Singh II, the founder of city of Jaipur and is just one of five astronomical observatories that he had constructed in several places.

The Jaipur Observatory was built between 1727 and 1734, at the time when he also built his new capital here.

Jantar Mantar is the best preserved observatory, as well as the largest still intact, and is a showcase of the architectural, cosmological and astro-logical skills and wisdom of that time.