Question: Through which important cities the does the river originating from the Duwamish, flow?
SPARQL:
SELECT DISTINCT ?uri WHERE { ?x <http://dbpedia.org/ontology/source> <http://dbpedia.org/resource/Green_River_(Duwamish_River)> . ?x <http://dbpedia.org/ontology/city> ?uri  . ?x <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/River>}