What is {coordinate location} of {Elbe} that is {applies to part} is {river mouth} ?
What is coordinate location  of  Elbe  that  applies to part  is  river mouth ?
SELECT ?obj WHERE { wd:Q1644 p:P625 ?s . ?s ps:P625 ?obj . ?s pq:P518 wd:Q1233637 }
select distinct ?obj  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q1644> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P625> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> ?obj .
?statement <http://www.wikidata.org/entity/P518> <http://wikidata.dbpedia.org/resource/Q1233637>
} 

The coordinates of Elbe near the river mouth?