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Geography and Climate
Dominating the world's surface is the Blue Sea, a body of saltwater broadly divided into quadrants: the East Blue, the West Blue, the North Blue, and the South Blue. These divisions are formed by two natural barriers that bisect the world at roughly perpendicular angles:
- The Grand Line, a relatively narrow strip of ocean infamous for its unnatural, rapidly-shifting climates and monstrous wildlife—as well as being enclosed by the completely wind- and current-free Calm Belt regions.
- The Red Line, a huge (and mostly barren) landmass that functions as the world's only true continent.
All parts of the Blue Sea—Grand Line and Calm Belts included—contain numerous islands supporting many different degrees of life. Travel between these islands is relatively simple in the four Blues, but significantly more complex in the Grand Line, where (in addition to the aforementioned hazards) many islands produce unique magnetic fields that render the magnets of ordinary compasses useless, necessitating special "Log Pose" compasses.
(North and South poles, both reputedly very cold, have also been stated to exist. It is unknown where they are located, or whether they contain the actual magnetic poles that control compasses outside the Grand Line.)
Said to be a giant sea route which circumnavigates the world, it is the one sea where normal compasses fail. It is the destination of every pirate and the path that leads to unimaginable adventures. Most of the story is based in the Grand Line. The reason this sea is sought by a large number of pirates is that the greatest treasure "One Piece", left behind by the legendary pirate Gol D. Roger, is said to be on the final island of Grand Line ("Laugh Tale"). The Grand Line is divided into two halves by the red line. The first half, known as "Paradise" to the residents of the second half of the Grand Line, is wildly unpredictable and dangerous, but pales in comparison to the second half. The next half, which is said to be much more difficult and dangerous than the first half, is the "New World". The Four Emperors unofficially rule the New World.
The Calm Belt is a sea area that surrounds each side of the Grand Line. No winds or sea currents can be found there, hence the name "Calm Belt". As a result, sailing through it is extremely difficult, especially because it is the nesting ground for the Sea Kings. However, Rayleigh swam from the Grand Line to Amazon Lily in the Calm Belt by himself after his ship was sunk in a storm.
The Red Line is the one and only continent in the One Piece world. It traverses the entire world from north to south. The Red Line separates the two oceans into four smaller seas. One of the oceans forms the two seas, East Blue and South Blue, and the other one forms the North Blue and the West Blue. The Red Line is used by those traversing the Grand Line to separate the first half of the Grand Line and the "New World", as well as the initial starting place of one's journey through the Grand Line; it also exists as the only way to enter the Grand Line besides traveling over the Calm Belt, a highly dangerous prospect. The Holy Land of Mary Geoise is located on the Red Line, at the part where the Grand Line meets the "New World".
Depth-wise, the Blue Sea ends at the Sea Floor, a constant landmass formed of the world's crust. Here, the Grand Line becomes somewhat less distinct from the other seas (though the Red Line remains largely impassable); aquatic life thrives in countless varieties, existing alongside volcanoes and trenches.
The Sky Ocean is a place that is unknown to most people in the Blue Sea. The reason for that is that the Sky Ocean is entirely made of clouds, which from the Blue Sea does not look like an ocean. The Sky Ocean clouds, however, are no normal clouds. There are two kinds of clouds, Sea Clouds and Island Clouds. Sea Clouds are just like water, which means that it can be sailed on if the ship is not heavy enough to sink through it, whereas Island Clouds are dense enough to carry all kinds of things.
There are different ways to get to the Sky Ocean from the Blue Sea. The only way that has been shown so far is the unorthodox and dangerous way in which the sailors have to take a Knock Up Stream, though it has been said that there is a second, slightly less dangerous way, called High West. In the Sky Ocean there are two known seas, the White Sea and the White White Sea.
- Further information: World Timeline
How long the world has existed is currently unknown. The largest figures of time given thus far have been speculative (and possibly hyperbolic) references to how certain natural phenomena may be "tens of thousands of years" old. Reference has also been made to an "ancient" age of dinosaurs, though it remains unclear whether this age is meant to have predated humankind as a whole.
The Great Kingdom existed until 800 years ago, when 20 Kingdoms fought and overthrew it. The one hundred years leading up to that was known as the Void Century, as no records of the events are kept with the exception of the Poneglyphs. After the Void Century, the World Government was formed by these 20 Kings. 19 of their families, including the Donquixote Family, moved to Mary Geoise, while only the Nefertari Family stayed in their original kingdom, the Arabasta Kingdom. The World Government banned research on Poneglyphs and covered everything that happened in the Void Century.
500 years ago, Oars appeared and caused chaos in the world; he would later be killed by frostbite.
400 years ago, a man named Mont Blanc Noland visited Green Bit, Vira and later Jaya. He went home to Lvneel to report his findings to the people. Unknown to him while he was away, half of Jaya was knocked up to the sky. When he returned with the king of Lvneel and his royal guards, he finds everyone and Shandora gone. The enraged king believed Noland to be a liar without hearing his side of the story, and Noland was executed and branded a liar. This would haunt his family up to the present.
Sometime before 28 years ago, Gol D. Roger began his piracy career. 28 years ago, he began his final journey that lasted 3 years. Afterwards, he disbanded his crew and turned himself in. 24 years ago, he was executed in Loguetown and began the Great Age of Piracy by offering up his treasure, the One Piece.
Monkey D. Luffy set out to begin living a life of piracy. His crew became notorious across the world as they took down two Warlords of the Sea and the secret government organization CP9, as well as destroying the judicial island Enies Lobby. However, they appeared to be exterminated by Bartholomew Kuma on Sabaody Archipelago, but were really split up and sent to different islands.
During this time, the pirate Marshall D. Teach, better known as Blackbeard, captured Portgas D. Ace in order to become a Warlord of the Sea. The World Government decided to execute Ace in order to incite a war against Whitebeard, and this was talked about the world over. Before the execution, however, the World Government suffered a major blow when Luffy broke into Impel Down to save Ace and led 241 prisoners in a mass breakout, and had managed to do so with the help of the Warlord of the Sea Boa Hancock. Blackbeard would then go and break out several more of the most dangerous prisoners.
This did not impede the planned execution of Ace, however, and the world became further shocked when they learned that Ace was the son of Gol D. Roger and Luffy was the son of Monkey D. Dragon. The Whitebeard Pirates arrived at Marineford and took on the Marines, but Ace and Whitebeard were eventually killed. However, Whitebeard announced to the entire world that the One Piece was real, and things only got worse for the World Government as Blackbeard arrived and took Whitebeard's power, announcing that this was now his age. Shanks then arrived and ended the war, as Luffy managed to escape with the help of the Heart Pirates. The strain from the Summit War of Marineford was such that it convinced two renowned veterans of the Marines Fleet Admiral Sengoku, and Vice Admiral Monkey D. Garp, to retire from their duties, and convinced Smoker to transfer to G-5 to keep a closer eye on the New World.
Over the next two years, great changes began taking place. Whitebeard's revelation began a new age of piracy, and Blackbeard usurped his position as one of the Four Emperors. Sakazuki became the new Fleet Admiral of the Marines, and the Marines relocated their base to the New World. The Marines drafted in new recruits worldwide to fight the ongoing threat of piracy, notably two new admirals, Issho and Ryokugyu, while Kuzan had left the Marines and appeared to have sided with Blackbeard. The Straw Hat Pirates returned after training for two years, and they entered the New World.
In the New World, the Straw Hat Pirates formed an alliance with the Heart Pirates to take down the Emperor Kaidou, and their notoriety only grew when they took down Donquixote Doflamingo of the Seven Warlords of the Sea and captured his subordinate, Caesar Clown; Doflamingo considered his defeat to be the tipping point that would set off a chain of battles for supremacy over the seas. Three Supernova crews, the Kid Pirates, On Air Pirates, and Hawkins Pirates also made headlines when they formed an alliance to take down Shanks. Similarly, the Firetank Pirates aligned themselves with Charlotte Linlin, and Capone Bege ruthlessly carried out her orders. Figures in the Underworld were emerging and beginning to stockpile deadly weapons, and the Revolutionary Army investigated these ominous happenings.
Society and Culture
In the Grand Line, there are islands which have their own climates and natural occurrences, such that people on these islands will dress to match it. Some islands in the Grand Line have unique cultures, such as Water Seven, Dressrosa, Arabasta, Sabaody, Longring Longland, Jaya, Skypiea, and Wano.
Compared to the Grand Line, there is less cultural diversity seen out in the North, West, South and East Blues. However, these oceans still have secluded islands and other locations with their own separate cultures and lifestyles, such as Kano Country in the West; Torino Kingdom in the South; Shimotsuki Village and Tequila Wolf in the East.
The world of One Piece appears to have a universal spoken and written language which seems to be a combination of Japanese and English. There are even instances of words or pronunciations from both languages being used together in either forms of written text, such as with the names used for the ships of the Yonta Maria Grand Fleet. English seems to be the most predominant written text in most parts of the world, especially outside the Grand Line, however signs of both of the written forms of these languages co-existing can be seen in many parts of the world on either signs, clothing, documents etc..
Even high above in the Sky Islands and deep below in the Sea Floor the universal language exists. In Skypiea, the English text seen on the surface seems to be common among the residents of Angel Island, but the Birkans seen residing in Upper Yard are known to use Japanese characters instead, such as in their trials and main temple. In Fish-Man Island, the universal language is also used, with both English and Japanese words and text being used throughout the island. The island of Dressrosa notably uses a lot of real life Spanish terminology alongside the world's universal language. Sanji and a few other characters have been known to use non-English/Japanese words on rare occasions or in the names of their attacks, with Sanji commonly using French, though its origin is unknown as no one in the Baratie or Germa Kingdom uses words from said language. There also exists an ancient language written on the Poneglyphs by the ancient stonemasons of Wano Country that only the scholars of Ohara could translate.
The enforcement of a universal language is largely due to the World Government and it's influence. When countries get involved with them, whether intentionally or not, they are forced to switch to the universal language and abandon any other languages they may have. In a small country in the North Blue, they went as far as to kill or exile anybody that refused to either abandon the language or become a slave to the World Nobles. 
Concludes non-canon section.
- Further information: World Government
With the fall of the Great Kingdom 800 years ago, 20 Kingdoms united to form the World Government. Most nations across the world are member nations of the World Government, although some nations are completely independent such as Wano. Mostly, it is up to each island to govern their daily affairs, although the Marines are stationed across the world to police the seas, and their authority extends to any member nation of the World Government should they be stationed on one. Usually, the World Government only gets involved when dealing with a person or event affecting multiple locations.
- Further information: Religion
Various people and civilizations in the world follow a vast array of religions, and various allusions to gods, devils, and religion have been made through architecture and speech. Despite the lack of any explicit mention of real life religions, there are several references to Christianity and occasionally Buddhism, with many churches, crosses, cathedrals, shimenawas and people dressing up in a religious fashion appearing throughout the series, along with instances of mentioning God, the Devil and Buddha from time to time.
Many people have their own personal beliefs and philosophy about what is right and what is wrong, as well as their own gods to worship. There are regions with pagan religions such as ancient Jaya, where people worshiped snake deities and later ancestral spirits. In Skypiea, the people worship Vearth. In Elbaf, they have different gods. In Thriller Bark, when the Straw Hat Pirates found a floating barrel, Usopp believed it was an offering to a sea god that they must pray to before opening it. The World Nobles' names always begin with "Saint". These are but a few of the many examples seen in the series.
Early One Piece
A world map was sketched by Eiichiro Oda when the series had reached the Loguetown Arc. Incomplete versions of this map were initially published in 2010 as part of "One Piece Grand Countdown" in Shonen Jump as well as the databook One Piece Green: Secret Pieces. The full map was finally published in One Piece Magazine Vol.9 in 2020.
This map includes a location called Corkwood (コークウッド Kōkuuddo?), a cliff with a height of 10 kilometers near Reverse Mountain, as well as a World Government building known as King's House (キングスハウス Kingusu Hausu?). It is unknown whether these locations exist in the canon story, as they have yet to appear in the series.
- Ohara's Tree of Knowledge, before its destruction, contained a geocentric model of the world with six natural satellites (which presumably includes the world's moon), one of which had a second body orbiting it. The world as shown in the model sits at a rough angle of about 24 to 25 degrees.
- It has been suggested that that there are over 20,000,000 islands in the world.