What were the Argonath?
I'm just going to quote :
The Argonath, also known as the Gate of Kings or the Pillars of the Kings, was a landmark on the northern edge of .
The Argonath consisted of two enormous rock pillars, carved in the likenesses of and facing to the north. Placed upon huge pedestals, each of the two figures held an axe in its right hand and its left hand rose in a gesture of defiance to the enemies of . The two statues stood upon either side of the River at the northern approach to .
The Argonath marked the northern boundary of Gondor.