SELECT ?arena ?arenaLabel ?maximum_capacity WHERE {

  SERVICE wikibase:label { bd:serviceParam wikibase:language "
   [AUTO_LANGUAGE],en". }

  ?arena wdt:P31 wd:Q641226.
  OPTIONAL { ?arena wdt:P1083 ?maximum_capacity. }
}

SELECT ?venue ?maximum_capacity WHERE {

  SERVICE wikibase:label { bd:serviceParam wikibase:language "
   [AUTO_LANGUAGE],en". }

  ?venue wdt:P31 wd:Q7463935.

  OPTIONAL { ?venue wdt:P1083 ?maximum_capacity. }
}