How many letters does the top answer for “home of aragonese castle” have?

The most common answer is ischia (6 letters).

Crossword clue: home of aragonese castle

1 answer found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

ischia 6 letters wd-fact-v3

a volcanic island (part of Campania) in the Tyrrhenian Sea at the north end of the Bay of Naples

home of belfast castle 50% similar → lowwood

home of chillon castle 50% similar → veytaux

home of hearst castle 50% similar → sanluisobispocounty

home of limassol castle 50% similar → limassolmunicipality

home of stormont castle 50% similar → ballymiscaw