The city is on the inside of the wheel. And bloods can walk around inside that wheel, just like normal. But you said that magic doesn't work, the closer you get to the spire. She shrugged again. But Sigil's an exception to that rule.
Magic works just fine there.
Some have speculated that it's a demiplane all its own, stuck inside of this one. I don't know, and it doesn't much matter. Gwydion eyed the spire again. That looks like quite a climb. The woman laughed.