Question: Where does the river end which starts in Richmond Park?
SPARQL query: SELECT DISTINCT ?uri WHERE { ?x <http://dbpedia.org/ontology/sourcePlace> <http://dbpedia.org/resource/Richmond_Park> . ?x <http://dbpedia.org/property/mouthLocation> ?uri  . ?x <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/Stream>}
Answer: The mouth location of the stream whose source place is Richmond Park is [River Thames, Petersham, London].