Key to the City

Key to the City is aquired from Pig Queen in the Palace. Once you trade with her one of the royal items (one being Royal Crown dropped by the Ant Queen, the other being Royal Scepter that is found in the Roc Robin island) she'll give you Key to the exhibition (this key has one use). Key opens a cabinet in the second chamber of the Palace. One cabinet contains Key to the City, the other one contains Can of Silly Things item (needed to build Skyworthy, counterpart of Seaworthy)