[ Frankfurt ] { flow: down; }
[ Ulm ] { offset: 6,2; origin: Bonn; }

( test:
  [ Berlin ]
  [ Bonn ]
  [ Frankfurt ]
  [ Hagen ]
)

[ Bonn ] --> [ Berlin ]
[ Bonn ] --> [ Ulm ]
[ Berlin ] --> [ Frankfurt ]
[ Frankfurt ] --> [ Hagen ]