Over them was a lane of pale-blue sky, around them the dark overshadowed River, and before them black, shutting out the sun, the hills of Emyn Muil, in which no opening could be seen. Frodo peering forward saw in the distance two great rocks approaching: like great pinnacles or pillars of stone they seemed. Tall and sheer and ominous they stood upon either side of the stream. A narrow gap appeared between them, and the River swept the boats towards it.
`Behold the Argonath, the Pillars of the Kings! ' cried Aragorn. `We shall pass them soon. Keep the boats in line, and as far apart as you can! Hold the middle of the stream! '
As Frodo was borne towards them the great pillars rose like towers to meet him. Giants they seemed to him, vast grey figures silent but threatening. Then he saw that they were indeed shaped and fashioned: the craft and power of old had wrought upon them, and still they preserved through the suns and rains of forgotten years the mighty likenesses in which they had been hewn. Upon great pedestals founded in the deep waters stood two great kings of stone: still with blurred eyes and crannied brows they frowned upon the North. The left hand of each was raised palm outwards in gesture of warning; in each right hand there was an axe; upon each head there was a crumbling helm and crown. Great power and majesty they still wore, the silent wardens of a long-vanished kingdom. Awe and fear fell upon Frodo, and he cowered down, shutting his eyes and not daring to look up as the boat drew near. Even Boromir bowed his head as the boats whirled by. frail and fleeting as little leaves, under the enduring shadow of the sentinels of Númenor. So they passed into the dark chasm of the Gates.
...
'Fear not! ' he said. `Long have I desired to look upon the likenesses of Isildur and Anárion, my sires of old. Under their shadow Elessar, the Elfstone son of Arathorn of the House of Valandil Isildur's son heir of Elendil, has nought to dread! '

(LoTR, II-9)