Urban Planning

Yes, I'm talking about designing your world based on historical templates.  The concept of urban planning may seem laughable to many of us when we have visited the narrow twisty streets of old European cities, but not all cities evolved in the same manner.  The traditional image that many of us have is of a village that evolved into a city over hundreds of years of evolution and accretion.  These burgeoning population centers may have started with muddy byways and slowly grown outwards over the surrounding countryside, which little thought to commerce or sanitation, but not all of them did.  Just as nations, cities arose in various ways.
   Military encampments of the Roman Legion formed a strict grid structure at the heart of many cities thought Europe.  Granted, once you get beyond the original boundaries of the Roman camp the purity of the grid tends to break down, but the root structure is there around what generally becomes the center of government.  Grid structures were popular in most cities that were built by intention, rather than happenstance, for obvious reasons.  These cities are easier to navigate.  They make it easier to transport goods, especially with broad diagonal boulevards cutting the grid.  It's also easier to quantify and regulate a population in a space that is carefully managed.
    Cities designed around governmental or religious buildings may have a radial pattern splaying outward from this central hub.  These outer layers serve both as support structures and protection for these central buildings.  Successive layers of ring walls may be built as the population expands.  Radial patterns are likely to form only part of the city's structure, as they require significantly more precision than the simple grid pattern.  Washington DC implemented a radial pattern with a series of circles as a part of a defensive plan for the city.
    Topography will often be the defining factor in how a city is laid out (especially if you don't have the technology or manpower to alter it).  Hills may encourage a radial pattern.  Homes built along a river might give a sinuous curve to their access road.  Defensive fortifications will often get the high ground while the commoners fill up the lowlands surrounding.  Markets develop along the riverside both because it's easier to transport goods there and because there may be season flooding along the banks.  Ground that is too highly sloped or a little rockier might just become the graveyard.
    Very few cities have been entirely planned from the outset (though DC and Brasilia are two), so they end up being a mixture of elements.  Have you gone to Manhatten and visited The Village after being so sure of yourself in Midtown?  Most planned cities grow beyond their original borders in a rather haphazard way.  Then again, many old cities have had cataclysmic events (The Great Fire, in London) that made it easy to redraw their maps in a more efficient manner, without evicting massive number of people from their homes and businesses (though not every nation has been averse to that). The simple layout of your city can be a colorful touch which allows you to discuss the history of your world and add significant layers to its character.


http://www.art.net/~hopkins/Don/simcity/manual/history.html
http://www.britannica.com/EBchecked/topic/619445/urban-planning
http://en.m.wikipedia.org/wiki/Urban_planning
http://munsonscity.com/tag/radial-grid/