How many {enclosure} are to/by {dome} ?
How many dome stadiums exist?
How many dome enclosures are there?
SELECT ( COUNT ( ?u ) AS ?d ) { ?u property:enclosure resource:dome }
SELECT (COUNT(?sub) AS ?subs ) {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> ?sub .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P3158> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> http://wikidata.dbpedia.org/resource/Q12493 .
} 

SELECT (COUNT(?sub) AS ?value ) { ?sub wdt:P3158 wd:Q12493 }
8