The oversized, bejeweled chair on which a king or queen sits is called a throne.
Monarchs — kings and queens — sit on thrones on special ceremonial occasions, and so do religious figures such as bishops and popes. You can also describe the act of naming a new monarch this way: "Queen Elizabeth II of England was throned in 1952." The word throne has its root in the Greek thronos, "chair or elevated seat." In ancient Greek mythology, Zeus was said to sit on a special heavenly seat, the Dios thronous.