The city in meatspace is composed of thousands of buildings, ranging in size from little cottages up in the mountains, through suburban mass-populated blocks, all the way to massive converted warehouses and megatall skyscrapers.
Every building is built on a plot and connected by road. All buildings are constructed by The Construct, who after all have a monopoly on that kind of thing. Megacorps will then buy these empty buildings from The Construct, and populate them with their employees. When you buy buildings from other megacorps, or sell them, you also take on or fire those same employees that inhabit the building.
You can see a summary of the building's properties, including its population capacity, and a brief architectural and historical description, by selecting it and clicking the info button.
Those buildings that are the headquarters of a megacorp have a flag on top with that megacorp's logo.
Every building in meatspace has a corresponding cybersite in cyberspace; pressing tab while a building is selected will switch to the cyber view, and show a different set of actions you can take in cyberspace.
You can only influence buildings within your sphere of influence.