We used to find something on an OS map, like a disused windmill or the like and just go out for a drive to find it.
Geoserchers now do somethng very similay with hand held GPS's, not the same as a map though.
I have, over the years, found a number of places, on various maps, where the roads and railways just stop, dead. They enter a "Black Hole", but the least said about those the better. When I went to see where one of those little country roads went, I was met at a very large gate, by a man with a very large item of ordanace, which, when waved in my direction,
had the effect of making me an expert in rapid 3 point turns and I could have used Wenchies Cloak of invisability to escape
. Never have gone back to see if they are still there.