The Goa Kingdom's symbol is a daisy with three feathers. Many nobles wear it somewhere and it can also be found on the police hats. A stylized form is also present on the high town walls.
This capital of the kingdom sits on the ocean-side, it is surrounded by tall walls. Gray Terminal lies just outside of the Great Gate and the kingdom itself is surrounded by the Mt. Colubo. The trash collected in the kingdom is dumped into the Gray Terminal.
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Twelve years ago, Luffy, Sabo, and Ace often came here to eat and would run away without paying. They would often run through the street to avoid authorities. Sabo himself was born in and comes from this kingdom. Eventually, the kingdom decided to burn down Gray Terminal in order to impress the approaching World Noble to increase their own social status. After the time skip, Sterry is now married to Sarie Nantokanette and is the king of Goa Kingdom, after the previous king has died under mysterious circumstances. The Goa Kingdom is to be represented at the Levely.
Dragon once referred to the Goa Kingdom's burning of the Grey Terminal as "A miniature blueprint for this world's future".
It shares part of its name with a state in India that was under Portuguese colonial possession before it was annexed. The name was often used collectively for all of Portuguese India.
According to Eichiro Oda, if One Piece was set in the real world, then Luffy would be from Brazil. Coincidence or not, like the Indian state of Goa, Brazil is also a former colonial possession of Portugal.
According to Luffy and Sabo, Dressrosa is similar to the Goa Kingdom, as both nations function through extreme class separation and discrimination caused by the royal families and nobles.
Despite its reputation as a peaceful rural kingdom, it had spawned several of the most infamous outlaws the world has ever known such as Dragon, Luffy, Ace, and Sabo.
↑SBSOne Piece Manga — Vol. 56 (p. 144), The real world country of Luffy is revealed.