One beer from the north of Germany, which remains rare, is hard to categorise. Possibly originating in Dortmund, but definitely from northern Germany, this strong, dark ale style (8-11% ABV) has similarities with some of the strong stock ales once found in the UK, and the oak-aged ales of Belgium.  Typically a little smoky, and definitely aged in oak for a time, it has a mild lactic edge.  Its demise coincided with the rise in popularity of lagered Bockbier, though a few examples have started to re-appear again in its home country.
(Bron: https://beer-styles.ebcu.org/germany/#Adambier)