Between 1727 and 1734 Maharajah Jai Singh II of Jaipur constructed five astronomical observatories in west central India. The observatories, or “Jantar Mantars” as they are commonly known, incorporate multiple buildings of unique form, each with a specialized function for astronomical measurement.
The Misra Yantra , the Samrat Yantra, JaiPrakash Yantra and Ram Yantar
The Misra Yantra is a composition of 5 instruments designed as a tool to determine the shortest and longest days of the year.
Samrat Yantra
The Jayaprakash consists of hollowed out hemispheres with markings on their concave surfaces
The Rama Yantra consists of a pair of cylindrical structures, open to the sky, each with a pillar or pole at the center. The pillar/post and walls are of equal height, which is also equal to the radius of the structure. The floor and interior surface of the walls are inscribed with scales indicating angles of altitude and azimuth. Rama Yantras were constructed at the Jaipur and Delhi observatories only.
( From http://jantarmantar.org/learn/observatories/instruments/rama/index.html)
The Ram Yantra
Samrat Yantra is a enormous sundial and is extremely accurate
During 1857 it was damaged and has been restored