But Germanicus also bestowed attention on other wonders. Chief of these were the stone image of Memnon, which, when struck by the sun's rays, gives out the sound of a human voice; the pyramids, rising up like mountains amid almost impassable wastes of shifting sand, raised by the emulation and vast wealth of kings; the lake hollowed out of the earth to be a receptacle for the Nile's overflow; and elsewhere the river's narrow channel and profound depth which no line of the explorer can penetrate. He then came to Elephantine and Syene, formerly the limits of the Roman empire, which now extends to the Red Sea.