Irem

Irem of the Pillars (Wikipedia entry) is a lost city located somewhere in the Arabian penninsula, and possibly also in the Dreamlands.

Howard Phillips Lovecraft describes it as having been built and then sorcerously concealed by King Shaddad (in contrast to the Koran, which says it was destroyed or removed by Allah due to Shaddad's wickedness). It is one of the centres of the world-wide Cthulhu Cult, the headquarters of the Arch-Hierophant of Cthulhu and located close to The Nameless City (home of a colony of degenerate Serpent People). Abdul Al-Hazred visited it at least once.

A possible location of Irem was located by ARCHINT in Oman in the late 1980s. A large meteor crater in Saudi Arabia may also be a candidate.