D&D 5E (2024) Sword Coast population data from 2024 D&D Pocket Expert

[Parmandur]

So, as a relatively recently radicalized Forgotten Realms Origonalist, I think the description from FR1 is sufficiently fantastical for my uses, particularly in contrast to the howling wilder wss the Sagvage Frontier actually was in the early Forgotten Realms:

 

[pukunui]

You know what would be a cool addition to waterdeep? An underwater district.

There are merfolk and sea elves living in the harbor.

 

[Henadic Theologian]

There are merfolk and sea elves living in the harbor.

Yeah expand it out to its own aquatic distinct.

 

[Parmandur]

Another point about Waterdeep farming: the inland, rural Desserin Valley has an entire economy about facilitating overland trade to Waterdeep and feeding Waterdeep. The Dessering Valley is about the size of the U.S State of Oregon...or to put it another way, about the same square milage as the United Kingdom. So, even Goldenfields aside, it isn't too crazy for a UK sized farming region to support a London sized city.

 

[Yaarel]

Another point about Waterdeep farming: the inland, rural Desserin Valley has an entire economy about facilitating overland trade to Waterdeep and feeding Waterdeep. The Dessering Valley is about the size of the U.S State of Oregon...or to put it another way, about the same square milage as the United Kingdom. So, even Goldenfields aside, it isn't too crazy for a UK sized farming region to support a London sized city.

Dont forget, the sea too can be farmed. Hence the Merfolk and Sea Elves.

 

[roguish]

One of the reasons it's so hard to estimate the population of pre-modern big cities is that the population was churning, people were coming and going all the time. They came in droves to find work and resources, to join kin and kith and compatriots (a big city is by default multiethnic), to be where the action is, to get away from some other place. And they left in droves to an early grave.

Seriously, the mortality in pre-modern cities was terrifying. A large chunk of it was due to disease, esp. contagious disease, which spreads so much easier in cramped spaces. It doesn't have to be as dramatic as the Black Plague, there are quite a lot of them! (I was idly checking recorded deaths in 1632 London, a non-plague year in the modern era, and more than 25% of them were from diseases we now have vaccines for.)

And another large chunk, as in the entire world before the 20th century (it's not city-specific), was due to child mortality. These numbers are staggering.

So in the real world, people mostly came to the city on purpose, and mostly left for reasons beyond their control. In a fantasy setting, the control goes to the worldbuilder. And the worldbuilder might decide that, for example:

• fewer diseases exist
• diseases are less contagious and lethal
• there are usually enough magic-users to contain the spread of a lethal contagion
• either way, when a hefty percentage of the city's population succumbs to disease, it's a plot point, not the norm
• there are enough healers willing and able to prevent those staggering numbers of child mortality
• under normal circumstances, magic and/or society is advanced enough to prevent large-scale famine and malnutrition, and to provide passable sanitation
• we're handwaving all of it because we're not making an elaborate well-thought "what if" scenario, we're only making a setting as background for a party of adventurers who kill things and take their stuff; all we really need is vibes

 

[Hussar]

They count the surrounding areas outside the city itself. Calimport does the same

Still utterly ludicrous. A city with no water sources in the middle of nowhere without the support of a massive empire is twice the size of Paris, Rome or pretty much any other of the largest historical cities?

There’s just no way.

 

[Hussar]

London reached a population of 2,000,000 in the mid-19th century...

Sure, once you have refrigeration and steam engines, you can do that.

With Renaissance level technology? Not a chance. Never minding the question of where did these people come from, the next question would be why? Why would Waterdeep be ten times the size of Baldurs Gate? There is just no logic there.

 

[Selas]

Still utterly ludicrous. A city with no water sources in the middle of nowhere without the support of a massive empire is twice the size of Paris, Rome or pretty much any other of the largest historical cities?

There’s just no way.

Then take it up with Ed Greenwood--the creator of the Forgotten Realms setting--who decided on this and put it in the 3E campaign book. Pages 177-180 if you happen to have it

However, keep in mind that Waterdeep is one of the riches city-states in the Sword Coast, and that the Forgotten Realms is a High Fantasy setting. The "Renaissance" technology is complimented by the High Magic available. It is a fantastical settlement after all, probably surpassed by places like Sigil

 

[Hussar]

And for people pointing to this or that city, the point is that these cities are the heart of massive empires covering enormous areas.

Waterdeep is not the capital of anything. There’s no empire nor is it even really master of any territory.

It’s more just an example of fantasy writers picking cool numbers than any real thought going into it.