Question: What is the largest city in the country where the San Marcos River originates?
SPARQL:
SELECT DISTINCT ?uri WHERE { <http://dbpedia.org/resource/San_Marcos_River> <http://dbpedia.org/ontology/sourceMountain> ?x . ?x <http://dbpedia.org/ontology/largestCity> ?uri  . ?x <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/Country>}