I don’t think code supports it, but you could have an if-then skip in the code for tile generation, so the tile only gets generated once. It would be acceptable to do it inefficiently, as simple as if it’s chosen, is it unique, has it existed, if no put the tile there, if yes re-roll the tile.
You may want to then add a normal location (a SUPERNATURAL shop, perhaps?) with items that can show the rare places, like a roadmap. Unfortunately, I don’t think there’s code to support the coordinates or compass directions in descriptions. It’s really bothersome because you can find the evacuation camp from the computer, but you have to go like 10 miles away to see it on the overmap. And I’m using a damn 2560x1440 screen with ascii glyphs.