Rhine21 The rock with the flag is called the Loreley. It stands 450' high and is the ultimate Rhinestone. It marks the narrowest and most treacherous part of the river. So much so that a legend grew up around a beautiful, golden-haired siren (the "Lorley") who would lure tired navigators to a destructive end. The actual cause, of course, was a strong current and hidden rocks under the water.