What they meant to print was “Skull Tower”, and it is a small but intense monument.  We have two cards available.  One is unused (Grade: 1, $4) and the other was mailed from Belgrade in 2019 with stamp and postmark (Grade: 1, $6).  Both cards have a sort of purple stamped “chop” placed by the museum itself and showing what might be individual numbers for each card.  Unique in that respect.