Segment for sessions, where users visited a specific area of website

I’m trying to create a segment for website visitors that saw content within an area of the site, denoted by a URL prefix (eg. /special-area), at some point during their visit.

This looks easy, I thought I could create a segment with a single condition:

“Page URL”, “Starts with”, “special-area” (or maybe “/special-area”)

This returns zero visits though. Am I doing something obviously wrong with the above? I’ve tried to use the documentation but not got very far.