ACCESS
Alan Madagascar wrote the equation that created the City, a formula that procedurally generated the world he saw every time he closed his eyes. He was able to transit into the place by simply constructing and solving the equation in his head. As he got older, he had trouble remembering the formula. He transcribed it into notebooks, so that all he had to do was input the final value to reach the other side.
Today, there are two ways to get into the City. Find a written copy of the formula, or derive it yourself. The former is the only hope a normal person has. The latter requires either extreme mathematical skill, lesser mathematical skill and a powerful computer, or a magick school fixated on architecture and buildings.
Either way, just drop a value in for X (the seed) and you’re off to the races. You must be inside a structure for this to work. Leave the building, and you’ll exit into the City.