Xuthal
"A weird, unreal atmosphere hung over all. Traversing this dim, silent palace was like an opium dream. Some of the chambers were unlighted, and these they avoided. Others were bathed in a soft, weird light that seemed to emanate from jewels set in the walls in fantastic designs." -- Robert E. Howard: "The Slithering Shadow"
An ancient city in the Southern Desert of Kush, also called Xuthal of the Dusk. The inhabitants were addicted to the black lotus and spent most of their lives in lotus-induced dreams.
Deep beneath the city, a shadow-demon named Thog slept, rising on occasion to devour some of the city's inhabitants. South of it were grasslands.
The city was built over an oasis, which the founders of Xuthal found in their wanderings. They came from the east, so long ago that not even their descendants remember the age. The city is really one great palace, with every building inside the walls closely connected with the others. One might walk among these chambers for hours and see no one. At other times, one would meet hundreds of the inhabitants.
The people of Xuthal manufacture their own food out of primal elements. They are wonderful scientists, when they are not drugged with their dream-flower. Their ancestors were mental giants, who built this marvelous city in the desert, and though the race became slaves to their curious passions, some of their wonderful knowledge remains.
References: The Slithering Shadow.