Trap street

You may be looking for the alien refugee camp given this title.

A trap street was a fake street inserted onto a map by a cartographer for the purposes of preventing or identifying copyright infringement. As Clara Oswald described it, a trap street was "a cartographer uses a fake street, throws it into the mix [of street names], [and] names it after one of his kids or whatever. Then if the fake street, "the trap street," ever shows up on someone else's map, they know their work's been stolen."

Clara later identified an alien refugee camp run by Ashildr as 'the trap street', owing to its apparent similarity to actual trap streets - namely, it existed on maps, but seemed to not exist in reality (as a result of its misdirection circuit). (TV: Face the Raven)