Board Thread:Suggestions forum/@comment-29212138-20170526182111/@comment-25101089-20170527222522

MrHobit1234, the Mountains of Harad do exist in Tolkien's works. They were called the Grey Mountains (not to be confused with the more well-known mountains of the same name in the north) and were part of the original, symmetrical creation of Middle-earth: Blue Mountains in the northwest, Red in the northeast, Grey in the southwest, Yellow in the southeast. (With the Mountains of the Wind in the eastern midmost regions.)

True, there is no mention of them existing in the Third Age, but nor is there any reason to assume they were destroyed in the cataclysms of Elder Days. The Blue Mountains were affected because of their closeness to Beleriand, and even then they were not fully destroyed, only partly ruined.