I grew up in Munich in the '80s. We detected back in the late '70s even, and we went everywhere. My buddy and I went straight through the Englischer Garten, no problem. No one knew what metal detecting was. All these old people walking in the woods would tell us about the war. One guy told me where old flak positions were, one person showed us where an American bomber crashed (and where it dumped all it's bombs, which explained the line of bomb craters through the woods), one person told me where he'd been on a detail at the end of the war, burying milk cannisters of gold items. I never pursued that one. Would have been too deep to detect and wouldn't know what to do with it if I did find it. One of the first finds was a British 30-pound incendiary bomb that hadn't burned. My buddy set a towel an fire and slightly burned his hand when he tried to clean a piece of the fuze that had phosphorus crust on it. I can't tell you how many stick incendiaries I found. I also found a roman coin and some interesting nazi items but I passed up a huge rough signal under a tree root that my newbie detecting partner then dug up: three different Nazi belt buckles and some K98 rifle ammo clips. The brass was still shiny. It must have been someone's collection even during the war and they buried it when the Allies took over. I rue that day. Overall, I didn't do very well, especially considering the possibilities. Even here in the US it's that way. My wife found a "US" belt plate in the creek behind our house in VA and she just left it on the bank. Someone took it of course. I'd be surprised if anyone in Germany objected to metal detecting, but you definitely can't detect on or near historical sites, even back then.