Jantar Mantar Observatory
Because the sun is so bright, we can only see the sun during the day, and the stars only shine at night. What would the sky look like, if you could see everything - the sun, moon, planets and stars - all together during the daytime? That is the basic idea behind Kapali Yantra, and indeed behind most observational astronomy before the invention of the telescope.
Kapali Yantra consists of two sunken hemispheres (bowls). A map of the heavens is engraved on each bowl (a different map on each), showing the positions and motions of various heavenly bodies throughout the year. Two wires (not visible in this photo) are arranged to cross above the surface of the bowl. The shadow of their intersection gives the position of the sun, projected onto the celestial map engraved in the bowl. This allows the observer to determine the position of the sun relative to the planets and zodiac at any time of the year, for use in horoscopy and other astronomical calculations.