“6: Have you not considered how your Lord dealt with Aad – 7: With Irem of lofty pillars – 8: the like of which has never been seen in the Land”?
[Q’uran, Ch. LXXXIX, 6-14]
Irem of a thousand pillars (Iram ḏāt al-`imād in Arabic), a city the like of which has never been built in the whole Land (according to the Q’uran) is a lost city shrouded in mystery. According to Islamic lore, King Shaddad, the son of Ad, had the city built as an imitation of Paradise on Earth to compete with God, and received for this heavenly chastise.
In some versions of the myth, Shaddad and his tribe of giants (or according to some other legends, with the help of a legion of demons (Jinns) built Irem before the time of Adam, thus making it the oldest city on Earth.
The exact location of Irem is somewhere lost in the Empty Quarter, the desert of Rub al Khali of Southern Arabia, where only by chance can Irem be found by the uninitiated.
Irem also plays an important role in the Necronomicon Mythos. The fabulous author of the “Al Azif”, the mad poet of Sana’a Abdul Alhazred was credited by Lovecraft for visiting Irem and penetrating its hidden vaults:
“Irem Zhat al Imad, Irem of the Pillars, the great city. I have spent ten years in the heart of the "Roba al Khaliyeh," the empty space, the great southern desert colored "Dahma," crimson. And I have seen the fabulous many pillars of Irem and I have been called "majnun," mad and possessed of the Jinn. Many are the strange and unbelievable marvels that may be seen there. Alas for the earth has swallowed up the City of Pillars, no more do the caravans of frankincense pass by. Many have called it a town of great wickedness, but do they dare comprehend the fabulous?
Irem was an earthly paradise to the initiated. Towers rising high, the great octagonal fort, alas no more! And there were places here of hidden knowledge and of power.
Some say it was built by giants, some by the tribe of Ad, but Irem was here before men and though swallowed she will protect her secrets from the profane, releasing them to the knowing
For there are many levels of existence for Irem, many levels of reality. So Irem of the Old Ones still exists in some form, and is not this great desert, this empty quarter connected to the void.? Cannot a Muqarribun interact with its unseen denizens in the Crimson Desert?” 
The tribe of Ad mentioned in the Q’uran bears a close resemblance to the Biblical Nephilim, which were also believed to be a race of giants and credited for building the City of Enoch. In some other traditions it was Cain, the murderer of his brother Abel to found the great city (Genesis, 4,17) which is somehow identified with Baalbek (Heliopolis) in what is today’s Lebanon.
In one of the earliest Arabic accounts of Irem, quoted by Mas’udi in “The Meadows of Gold”, an other striking identification of Irem is proposed with the city of Damascus in Syria:
“Such was the reign of Djeiroun, the son of Saad, the son of Ad, who first settled in the Country of Damas, where he had his capital. There he gathered a great many pillars of marble, white and coloured and had a considerable construction built which gave the name of Iram of Pillars...Many historians give different opinions on the account of Irem and its location, but I believe that to this day, in the year 332 of Egira, its ruins survive in what is now one of the markets of Damas, close to the door of the Mosque-cathedral called Djeiroun or Gate of Djeiroun.” 
Another interesting reference to Irem in the work of Mas’udi appears in the chapter describing the foundation of Alexandria by Alexander the Great. According to Mas’udi, when Alexander reached the site of what was to become the capital of his new empire, he found the place marked by a great many ruins in the middle of which stood a column of stupendous size bearing an ancient inscription “in Mosned characters, that is to say, in the ancient writing of Himyar and the kings of Ad”. The inscription read:
“I Shaddad, son of Ad, son of Shaddad son of Ad, whose arms have embraced the Earth, I had large columns cut from the mountains and quarries, I built Irem of pillars, a city the like of which was never seen, and after that, I decided to build a city similar to Irem where I gathered all the noblest and fairest of men, the very best of all nations and tribes, because this place was protected by Fate from all disasters and calamities which befell the Earth. But in this grand endeavor I was stopped and thus was my project abandoned […] It was not in front of a mighty king or his innumerable legions that I surrendered, but to Death only because the end of my days had come by the mercy of God”
 Al Azif, Necronomicon, Book of Places, from http://www.chaosmatrix.org/library/books/necro_proj/
 Al Mas’udi, “The Meadows of Gold”, 956 AD, ch. XLVII, ed. Fr. “Les Prairies d’Or”, vol. III, p 271,
 Al Mas’udi, cit. ch. XXXVII, vol. III, p. 79
 O’Connor, David, “The Location of Irem” in The Journal of Egyptian Archaeology, Egypt Exploration Society, 1986
 Leake, Johnatan “Lost Atlantis of the Desert runs into sands of doubt”, The Sunday Times, 20 October 2002
 Laurence Galian, The Sun at midnight, Quiddity, 2003