In the 1730s the Rajput king of Jaipur, a great fan of astronomy, had the Jantar Mantar complex built. It consists of almost 20 open air astrological and astronomical structures that are actually sophisticated and very accurate instruments measuring the passage of time, the seasons, the planets, and the stars and constellations. The result is a remarkable architecture and design. This sunken hemisphere measures the sun’s passage–along with a twin device for the southern hemisphere–through the heavens during the year.