The Crystalline Caves of Black Leaf Forest

From the introduction:

In the Crystalline Caves of Black Leaf Forest there is an entrance to the dark elf city of Ithilanx, a city radiant with precious gems and minerals far beneath the earth. The entrance is a set of gold double doors that have magical writing on them, and it is protected by drow of the House of Imazress, a dark elf house of Ithilanx. The magical writing describes how to open the gold double doors, and beyond them is a tunnel that is miles and miles long that goes to the dark elf city of Ithilanx.