As Above - So Below
Waterdeep, also known as the City of Splendors or the Crown of the North, is the most important and influential city in the North and perhaps in all Faerûn. For this reason it was considered part of the Western Heartlands of the Realms, even though it lay 150 miles north of Daggerford on the shores of the Sword Coast. The city sat "slightly above the 45 degree north latitude line on Toril." The road to Waterdeep was well paved and well patrolled. The city was the hub of trading from the mineral-rich lands to the north, the merchant kingdoms of Amn and Calimshan to the south, the kingdoms of the Inner Sea to the east, and the sea kingdoms and traders to the west. Waterdeep's authority extended between thirty to forty miles from its walls. The surrounding region had a population density of over 200 people per square mile.
Waterdeep was named for its outstanding natural deep-water harbor, and the city that grew up at this site became the commercial crossroads of the northern Realms. More than 100,000 people made their home in Waterdeep. The city sprawled northward from the sea, spreading along the flanks of Mount Waterdeep, which used to be home to the Melairkyn, a mithral-mining dwarven clan, and the entire length and great depth of the mountain was riddled with passages and tunnels, most of which were occupied by deadly creatures whose presence in the mountain predated the founding of the city itself. The halls of Undermountain located beneath the city were a popular target for adventurers, who enjoyed the close vicinity of the city's main taverns and temples where aid could be purchased through donations.