You would be surprised. Having spent a lot of time between Germany and Poland you can go for a hike in the woods and still run in to some collapsed old bunker that still have old military gear that no one has known about for ages. Heck, there was even a major crisis in Berlin a few years back when an unexploded bomb was found in the basement of a brothel and they had to shut down the red light district. Talk about Mayhem.....
Except that a train would be on rails. Hard to hide for 70 years.