Triton

Triton is the only terraformed world of the Neptune Subsystem and thus is considered its capital by default. It is also somewhat unique among the Outer System worlds in that it doesn't necessarily had to be terraformed in order to maintain its population, although it still was.
This concludes the list of interesting facts about it.

Geography

Two large oceans with a continent in-between. Some plains, some mountains of varied range, some small rivers and lakes. Nothing particularly notable.

Climate

A largely standard Outer World. Extremely high humidity and extremely stable temperature caused by the fact that said temperature is less reliant on the sunlight and more on the extreme amounts of greenhouses gasses in the atmosphere, which remains stagnant.
The only notable thing about it is that there is some temperature variety tied to the rain. Upper layers of the atmosphere are exposed to the cold vacuum of space enough to regularly freeze and fall down as snow. Usually it melts before it touches the ground, but it will still cause a temporary drop of the temperature.

Fauna & Flora

Almost none. Neptune Subsystem is the furthest place in the Solar System where there's enough light to make the most basic of plants grow. Lichen, fungi and algae are the peak of local flora, and as you can expect, it's not enough to maintain complex fauna.

History

Triton being so far from the Inner System made it an unpleasant place to live for humans. While it was terraformed, the decision to do so was heatly debated and did lead to an investigation into the exact thought process behind it, as it was seen as a waste of precious nanites.
Triton remained Solar System's unwanted child for about a decade until the rise of the transhumanism. While the planet was hardly a decent place to live for being of flesh and blood, its low gravity and limited sunlight weren't an issue to the Virtuals.
Today Triton is the capital of the Cybernetic Union. While most of its inhabitants live on other moons of Neptune, Triton is the one place where biological humans can actually visit to directly interact with the Virtuals.... or become one of them.

Triton
Summary
Distance from Sun: 4500 million km
Distance from Neptune: 0.355 million km
Diameter: 3067 km
Solar Constant: 0.00218
Mass: 0.00359 Earths
Gravity: 0.0794 g
Mean Density: 2.061 kg/l
Orbital Period: 164.8 Earth years
Day Length: 5.877 Earth days
Rotation Axial Tilt: 130 degrees (40 degrees, retrograde)
Avg. Temperature per Latitude
poles: 14.7 C
75 deg: 15.3 C
60 deg: 15.5 C
45 deg: 15.7 C
30 deg: 15.8 C
15 deg: 15.9 C
equator: 16.0 C

Astrography

Object Type: Icy Moon
Object Subtype: Terran Eccentric
Primary Location: Core Sector
Secondary Location: Solar System
Tertiary Location: Neptune Subsystem
Transshipment Station: Halimede

Habitation Status

Status: Colonized
Classification: Civilized World
Population: ~100 000.
Capital: Primary Data Hub
Government: Cybernetic Union
Solar Commonwealth Member: Yes.