It all boils down to money
From up close, Cael saw that it really was a castle at some point, and while it wasn't one now, the new owners only improved the security measures. The embrasures in the walls were walled off, the only gate was guarded by a pair of grim knights, and more patrolled the walls.
And it was there, on the outside of the gates, that Cael spotted a small but elaborately adorned booth with a signboard that said, "Library Tickets".
Since no other explanation was required, Cael came up to the booth, and the bored man who sat inside.
"Hello, signore. How much do tickets cost?"
The man perked up and gave Cael a disdainful look. "More than you can afford, swain! People like you, coming to our glorious city, then not bothering even shaving like they ought to…" His frown deepened even more. "Stole your clothes from somewhere probably, too…"