<Li> Unnatasha Yantra (a metal ring divided into four segments by horizontal and vertical lines, with a hole in the middle; the position and orientation of the instrument allows measurement of the altitude of celestial bodies) </Li> <Li> Vrihat Samrat Yantra (world's largest gnomon sundial, measures time in intervals of 2 seconds using shadow cast from the sunlight) </Li> <Li> Yantra Raj Yantra (a 2.43 - metre bronze astrolabe, one of the largest in the world, used only once a year, calculates the Hindu calendar) </Li> <P> The Vrihat Samrat Yantra, which means the "great king of instruments", is 88 feet (27 m) high; its shadow tells the time of day . Its face is angled at 27 degrees, the latitude of Jaipur . The Hindu chhatri (small cupola) on top is used as a platform for announcing eclipses and the arrival of monsoons . </P>

Who built the jantar mantar observatories in jaipur and delhi