Question: What structure in Downtown Chicago that was opened before 1930-05-12?
Answer(s):
answer: Wrigley Field
answer: Chicago Cultural Center
answer: Shedd Aquarium
answer: Field Museum of Natural History
answer: Art Institute of Chicago Building
answer: Navy Pier
answer: Museum of Science and Industry
answer: Cadillac Palace Theatre

SPARQL query:
PREFIX ns: <http://rdf.freebase.com/ns/>
SELECT DISTINCT ?x
WHERE {
FILTER (?x != ns:m.01_d4)
FILTER (!isLiteral(?x) OR lang(?x) = '' OR langMatches(lang(?x), 'en'))
ns:m.01_d4 ns:travel.travel_destination.tourist_attractions ?x .
?x ns:location.location.containedby ns:m.01_d4 .
?x ns:architecture.structure.opened ?num .
FILTER (?num < "1930-05-12"^^xsd:dateTime) . 
}