SELECT DISTINCT ?uri WHERE { ?x <http://dbpedia.org/property/material> <http://dbpedia.org/resource/Wrought_iron> . ?x <http://dbpedia.org/ontology/river> ?uri . ?x <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/Bridge>}
Bridges over which rivers are made of Wrought Iron?
SELECT DISTINCT ?t WHERE { ?e rdf:type ontology:Bridge . ?e property:material resource:Wrought_iron . ?e property:river ?t }
Potomac River, Cacapon River
The rivers crossed by bridges made by Wrought iron are [Potomac River, Cacapon River].
Rivers that cross iron bridges [Potomac River, Kakapon River].