Once called the "Queen of the Danube," Budapest has long been the focal point of the nation and a lively cultural centre.
Hungary is called the "Queen of the Danube"
Budapest, not Hungary, was once called the "Queen of the Danube." I think this tricked the system because Budapest is the capital of Hungary
( z1 call :ARG1 ( z2 country :name ( z3 name :op "Hungary" ) ) :ARG2 ( z4 queen :mod ( z5 river :name ( z6 name :op "Danube" ) ) ) )