What would a perfectly planned capital look like in a world with space travel?

Question

In a world with limited space travel (basically, people can travel between different moons but not to other planets/galaxies), the ongoing form of government decided to build a perfectly placed Capital city for its nation, one that can house plenty spaceports for trading and military. What would it look like, in terms of geographical location and urban planning?

A few points I've considered before:

• Spaceships are big and require a lot of space to be "stored", so I imagined it should have a lot of vertical space, like those big vertical garages.
• At the same time, you wouldn't want the terrain for your perfectly planned city to be uneven. So you'd want the city to be on flat lands.
• How would you defend such city from spaceship attacks? A dome? How to make it so that commerce can easily come and go but you'd still have the advantage over enemy armies and ships?

Edit with more info:

• This is a sci-fi scenario with multiple alien species coexisting in the same system. They live in 4 different moons orbiting a gaseous planet. Big spaceships are used for traveling between moons and smaller urban ships are used in cities for daily activities. There are no other planets in this solar system, so space travel is restricted between moons.

Answer 1

It depends on the symbolic aspirations of the founders of your city

A 'Planned Capital City' allows the Urban Designer (or other entity placed in charge of design) or leaders to implement principles that are considered important to either the nation or the time. This is distinct to other city planning, as Capital Cities have both government and symbolic significance.

So, for instance Canberra was designed 'from the ground up' as a capital city for Australia: Canberra was envisaged as a capital that 'joins' all the state capitals together. Symbolically, these are represented by streets that meet 'in the middle' to where parliament sits (called 'Capitol' on the map above) with satellite functions elsewhere.

However it doesn't stop there - if you look at the 'capitol' you will notice that it is actually a small hill. This symbolically means that the most important aspect of Australia that joins everyone together is the land. The Flag or Australia is actually not planted in the hill, but suspended over it, symbolising this further:

Even parliament sits underneath this hill, with public galleries overlooking parliamentarians, symbolising again that member of parliament serves the nation, not the other way around.

So your Capital City, if planned from the beginning, will reflect the aspirations of your nation. If it is democracy, expect equal regard to all your moons. If it is dominance, expect monumental architecture accompanied by grand boulevards and very strong axis.

It is important to the leaders of your nation that the Capital City planning represents the nation, as opposed to a standard city, so expect the design of your city to represent these principles.

In fact, this would easily override other factors such as trade and defence, which would likely be relegated to outskirts of your city (although, having these on the outskirts of your city gives practical benefits too, allowing for expansion and large industrial and trade facilities not associated with symbolic centres in the middle).