Supposedly it's a SUPERMASSIVE sphere like structure called "The City" that stretches from the Sun to the Oort belt.
*Image that shows Betelgeuse overlaying the orbits of the solar system, which in turn is inside the black which is the Oort Belt...The City is bigger than orange overlay. Note: The sun is the small yellow dot in the middle*
This world contains rooms the size of planets (The main character/indestructible immortal badass, Killy, walks through a room the size of Jupiter) and it takes several months to hundreds of years to travel from one place to another on super fast elevators. This whole structure itself is being built into infinity by rampant building machines the size of neighborhoods. (Their building material is described as baryonic dark matter or something like that...I'm no physicist or civil engineer so I have no idea what that meant when the author said it)
*Jupiter Room*
*Elevator*
*Building Machine (Right) and Safeguard Titan (Left)(Explained next paragraph)
On top of all of this, there's a digital super AI/cyberspace called the "NetSphere" that spans the entire structure, and contains a little program called the "Safeguard". The Safeguard is like an "anti-virus" that deploys various security drones that range from hordes of drones to god like cyborgs to stop people from crossing over once thought to be indestructible walls called "megastructure" that divides up The City into nice little thousand mile quadrants, save people with special "Net Genes" that the main character spends thousands of years of his life trying to find.
*Lowest Class Safeguard Horde chasing down last remnant of humans in The City*
*First Class "immortal with relativistic abilities" safeguard*
Now my point of sharing all of this is this; is it possible for a structure of this size to exist/be built by an advanced race in the Universe? Could a programming system compute fast enough to respond instantaneously and intelligently over this massive of a space (Center of the Sun to outskirts of the Oort Cloud)? Would it collapse instantaneously into the Universe's biggest Void/Black Hole?
Or is this simply that? Science Fiction and completely out of the realm of this Universe.