Moondeep Sea

The Moondeep Sea is a subterranean lake approximately 240 miles wide found in the Underdark beneath the Galena Mountains. The cavern which contains it is known as the Vault of Gnashing Teeth, so named for the countless animated skulls stuck to the cavern's ceiling.

The moondeep sea is known for its giant aquatic spiders and the city of V'elddrinnsshar‎ which lies on a mile-wide island dominated by a plateau in the middle of the lake.