Question: Which sea is surrounded by Rostock and Kaliningrad?
SPARQL:
SELECT DISTINCT ?uri WHERE { ?uri <http://dbpedia.org/property/cities> <http://dbpedia.org/resource/Rostock> . ?uri <http://dbpedia.org/property/cities> <http://dbpedia.org/resource/Kaliningrad> . ?uri <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/Sea>}