He tells a story he can't finish because he's laughing so hard. Even Catherine knows what he's saying isn't true. And she was already expecting an abbey to be like what was in her imaginations - before she even left Bath we're told she was imagining herself in places like that!

She was to be their chosen visitor, she was to be for weeks under the same roof with the person whose society she mostly prized — and, in addition to all the rest, this roof was to be the roof of an abbey! Her passion for ancient edifices was next in degree to her passion for Henry Tilney — and castles and abbeys made usually the charm of those reveries which his image did not fill. . . . Its long, damp passages, its narrow cells and ruined chapel, were to be within her daily reach, and she could not entirely subdue the hope of some traditional legends, some awful memorials of an injured and ill–fated nun.