Dragon Temple

The Dragon Temple is the ancient fortress of what became known as the Dragon Army of Tiamat.  Built by Ice Dwarves, Drow, and the Sons of the Dragon under the orders of Kodarek the Dread, this massive castle at the northern most tip of Sundra serves as the home of the Dragon Cult.
After the Second Great Dragon War, most of the Dragon Army of Tiamat survivors, minus the Drow, retreated back to this temple.
With Kodarek the Dread defeated and killed by The Dragon Watch and Llolth, Queen of Spiders, returning to the Underdark, the Dragon Temple is still ruled to this day by Betewl the Beholder.