Robert E. Howard 
Jewels of Gwahlur [EPUB ebook] 

‘The cliffs rose sheer from the jungle, towering ramparts of stone that glinted jade-blue and dull crimson in the rising sun, and curved away and away to east and west above the waving emerald ocean of fronds and leaves. It looked insurmountable, that giant palisade with its sheer curtains of solid rock in which bits of quartz winked dazzlingly in the sunlight. But the man who was working his tedious way upward was already halfway to the top.’
The Teeth of Gwahlur are legendary jewels, kept in an abandoned city in the country of Keshan. Conan, following legends of this treasure, has travelled to the lost city, where supernatural gives way to intrigue.