Question: What tourist structure in San Diego that was opened before 1855?
Answer(s):
answer: Mission San Diego de Alcalá

SPARQL query:
PREFIX ns: <http://rdf.freebase.com/ns/>
SELECT DISTINCT ?x
WHERE {
FILTER (?x != ns:m.071vr)
FILTER (!isLiteral(?x) OR lang(?x) = '' OR langMatches(lang(?x), 'en'))
ns:m.071vr ns:travel.travel_destination.tourist_attractions ?x .
?x ns:architecture.structure.opened ?num .
FILTER (?num < "1855"^^xsd:dateTime) . 
}