Song City is the capital of the Song Dominion, on the planet Song. It's a huge, craggy, green, self-sustaining island in the sky, constructed that way in order to distance it from the radiation-laden ground. It's covered in huge, shining metallic spires and is lush with plant life of all kinds, in distinct contrast to the world below.
The 'island' was created with a Decheeran landmass generation technology, who developed it using their knowledge of solar energy and nanotech. This landmass (which the Decheerans call 'sunloft') is strong, porous, and scientifically lighter than air, resembling dark green cork. Sunloft is biodegradable when exposed to water, which is great for food production, though it requires constant upkeep and an influx of raw biomatter to replenish the substance of the island.
Many of the residential buildings in the city are crafted primarily from wood, another influence of the Decheerans. Massive hovertech engines (developed by the Amaians and the Ry'nari) keep the city in the air and stable, while force fields, controlled electrostatic discharge, and atmospheric manipulators keep the air clean and the wind quiet. Tech is in use everywhere, but wealthier residents prize discrete tech that doesn't make itself glaringly obvious.
Despite the serene, minimalist facade of the city, its inhabitants are painfully aware of what caused the wasteland below, which even eight centuries later remains mostly uninhabitable. As such, the Song Dominion is capable of fielding a ruthless military force when it needs to, and it has large clusters of military satellites in orbit around the planet, placed there to house their combined army and protect the capital from any incursions. Great gun emplacements are concealed beneath the spongy mass of the city itself, which could turn the whole thing into an island-sized, laser-shooting battleship in the sky.