Unnatansha Yantra .

 astronomical, place with historical importance

Construction of the instrument:
The Unnatansha Yantra is another circle instrument. It consists of an upright in a sort of gallows hanging bronze ring of about 5 m in diameter and graduation. The gallows is not aligned exactly north-south direction, but about 10-15 degrees to the left, presumably so you could have a clear view on the direction finding the North Star. The axis about which the Unnatansha Yantra is rotatable, the axis Zenith - nadir. A vertical and horizontal cross-shaped stiffening crosses the circle at the intersection and allows the attachment of a rotatable Peilinstrumentes at the county level, such as a gauge rod or tube, etc. (missing today on the device). This provides both axes perpendicular to each other, and any point in the sky can be targeted. May be due to the enormous size of the ring, the device is in a kind of depression hung with revolving stages, so that we are aiming not too uncomfortable from different positions.(source and more details.:www.bernhardpeter.de/Jantar-Mantar/seite516.htm)