This is a Dakhma. In English, a Tower Of Silence. It’s used to dispose of the dead - it is considered unclean to bury the dead in India because the body becomes polluted with the Avestan (corpse demon). So, they lay the dead at the top of these towers to decompose & be eaten by the birds so they can be cycled back into the earth cleanly. By doing this the bodies will become purified and no longer polluted by the corpse demon.