In reply to Darron:
Since about ten years there are wild Bison near where I currently work in Germany, halfway between Frankfurt and Ruhr area. One herd in an enclosure, and one herd roaming free.
The animals in the enclosure are impressive enough, but so far I have failed to locate the wild herd, even though I came across a recently trampled meadow on my mountainbike where I must have missed them by a couple of hours. They can be suprisingly invisible for such big animals!
Best chance to find them, though, is winter, when they can be stationary on some harvested fields. They do not normally release the location of the wild herd, but it pays off to see which local roads are suddenly closed. Better luck in November, I hope!
The area is also the only place in Germany with official "attention, bison crossing" road signs!
For the last proper free herds you have to go to Bialowiecza NP in Eastern Poland, but I did not get lucky there either.
CB