Amon SûlAmon Sûl - The southern outpost, also called Weathertop, for the Kingdom of Arnor.  It was destroyed destroyed by Angmar in the war with the northern kingdom and was a ruin by the end of the Third Age.

 

"On the western flank of Weathertop they found a sheltered hollow...On the top they found, as Strider had said, a wide ring of ancient stone-work, now crumbling or covered with age-long glass.  But the center a cairn of broken stones had been piled.  They were blackened as if with fire.  About them the turf was burned to the roots and all within the ring the grass was scorched and shriveled, as if flames had swept the hill-top..." ~The Fellowship of the Ring, Book I, chap. 11 (A Knife in the Dark)