You are allowed to travel abroad with under 10 000 euros without declaring it. As far as I know we do not have the same problem with asset forfeit laws like the US. There are no laws limiting how much cash you can have at home and while travelling. Though if you hoard millions in gold that is discovered in a police raid I think your main concern will be why the raid happend.
In the EU, laws differ by country, so I wouldn't categorically declare that it's legal everywhere to have any amount of cash at home or traveling. From incidental local news reports here in the Netherlands, I suspect that if I were found during routine checks to be traveling with multiple-10k cash in my backpack or in my car, it would be seized and be treated as illicit until I prove otherwise.