This is a Mercedes Benz G4 type W31. There are only a handful of known authentic examples to exist these days. Most were destroyed during WWII and it's aftermath. No doubt the ones that still exist are quite valuable. It was a heavy duty off-roader as well as a car that could be used for state uses. They also saw use in various military roles including medical wagons. Hitler would often ride in this type vehicle with his bodyguards who normally were carrying an arsenal of weaponry with them. Because it would go off-road and could also move at relatively high speeds it was a perfect vehicle for this purpose.
This wasn't the only car from Mercedes that Hitler had, but it is one of the more interesting vehicles made by that company. I don't say that because of it's infamous owner, but more for the rather impressive engineering behind it. This particular example was restored by MB a few years ago for the Spanish royal family that owns it. Hitler BTW was often seen in a MB 770K. It was a much more elegant vehicle than the G4.