World Building: Working in Realism

So I recently started up a new campaign set in a setting that I've built over the course of three years and spanning two other campaigns. This campaign has changed a lot since its inception, starting out as an incursion from the infernal realm to the apocalypse. Before I didn't do much preparation with the setting, but now I've gotten a bit more inspired. Today I will be going over what I did to create the city states of my world.

This might be a bit overkill, but sometimes its necessary to do research.

Overview

The world of Celestine has gone through a major upheaval in the last 150 years. Many of the original cities and villages have since been destroyed or abandoned. Out of the three original political powers from my previous campaign only one still exists and it is a shadow of its former self.

Instead of having giant kingdoms like I originally had most of the political powers are now City-States with most of them having little interaction with each other. The reason for this is that no City-State should require trade with another in order to survive.

For my example City-State I am going to focus on Elv, the City of Canals. If it isn't apparent this city is based on Venice.

Building Rome in a Day

Do not search how long did it take to build Rome, the result is about one million days (over 2000 years).

A better indicator might be what the Dungeon Master's Guide says on page 128 in the section "Building a Stronghold". Building a palace or castle will take roughly 3 years in my game world. Building a City-State shouldn't be too much longer than that.

The city of Elv was established as a trading outpost on a lagoon. After several years of good business the trading outpost built itself into a center of trade for the region. Elv wasn't built in a day, but it was built in several decades.

Population

Realistic populations are hard to gauge, historical references to famous City-States range from 60,000 to 100,000. While I would prefer to use real world numbers I found that the Dungeon Master's Guide also had an answer, up to 25,000. I prefer the 25,000 number myself even if it isn't realistic it does seem a lot more reasonable when trying to maintain a city.

Elv has around 23,000 people, with numbers inflating and deflating due to economic and seasonal changes.

To Battle!

In Warhammer 40,000 and several other fictional universes seem to have a trouble with scale of military conflicts. For reference I used Writing-World.com's article on keeping Fantasy armies realistically sized. I used a simple equation, 7% of the total population of the city could be drafted into the army without too much risk to destroying the city's economy.

With this in mind there are about 1610 people maximum could be deployed in the Elv military, we'll say that 800 are typically kept during peace time. Looking to the Player's Handbook a poor lifestyle requires 2 sp to maintain per day. So to keep this military strength would require 2000 sp per day. Which would cost around 64,000 gp per year to keep the military at this strength for the city. That seems a bit reasonable. I would like to pay the military enough for a modest lifestyle, but that would have been 300,000 gp per year. A possible way to mitigate this is with indentured servants and slaves.

Conclusion

Building a world is tough business. Its not necessary to go this in depth, but this does help me keep track of how big the world is. Feel free to take these tidbits to your campaign:

• Cities aren't built in a day, but the can be in several years.
• Population of cities should be sustainable.
• Keep army sizes sustainable as well. An army should rarely reach more than 7% of the total population.

As always post any comments, questions, and critiques below.