The Inner Sea is the trading and cultural hub of two continents of Golarion, Avistan and Garund. At the heart of its waters stands Absalom, the City at the Center of the World. This ancient island city-state has survived nearly 5 millenia of toppled kingdoms to thrive as a have of merchants and scoundrels. In the west, the Inner Sea passes through the narrow Arch of Aroden, a tenaciously contested strait named for the monolithic ruined stone bridge connecting the two continents at their closest point of approach, into the Arcadian Ocean. To the east, the Inner Sea opens into the vast Obari Ocean.
Generally speaking, civilization centers on the Inner Sea, with barbarism and savagery taking hold where the sea’s refining influence wanes. Exceptions exist, of course, and the scattered lights of civilization stand out in the dark wildernesses and savage frontiers far to the north at the top of Avistan and well to the south in eastern Garund. Likewise, dark, wild areas exist within otherwise civilized lands close to the Inner Sea. Mercenaries and would-be heroes seek fortune and glory throughout the Inner Sea region, uncovering lost treasures, pacifying terrible dangers, and finding ignoble deaths in every unclaimed wilderness, kingdom, and empire of Avistan and Garund.
North of Avistan stretches the Crown of the World, a massive sheet of ice and snow that links the continent with others in the northern hemisphere. Where the two meet, hardy barbarism tends to dominate. Even in northern kingdoms that strive for advancements in civilization, the use and knowledge of arcane magic remains relatively unknown and certainly mistrusted in places such as the Lands of the Linnorm Kings and Realm of the Mammoth Lords. Even Mendev, a relatively advanced nation filled with pious crusaders, seems to shy away from arcane magic.
Magic becomes more common in the southern nations of Avistan, particularly in the devil-binding empire of Cheliax and its former colonies and vassal states. The ruling caste of shadow-haunted Nidal is suffused with forbidden magical forces, while the elves of Kyonin practice fey rites that date back millennia. On Avistan’s rocky northwest shore, the Varisian frontier boasts the mostly intact ruins and lost magics of lost Thassilon – as well as the famed Acadamae wizarding school.
Use of magic and the appearance of the fantastic and bizarre are much more commonplace on the southern continent of Garund. In the deserts of Osirion stand countless monuments to near-forgotten pharaohs, godlike beings who raised their people from barbarism to the heights of ancient empire. Along the eastern coast stand the remnants of Nex and Geb, two kingdoms formed to serve opposing wizard-kings in the distant past. Today, Geb relies on animated corpses to harvest food for its living inhabitants. The courts of Nex boast the most advanced and least-understood schools of arcane learning on the planet. Between these former enemies lies the magic-dead stretch of desert known as the Mana Wastes, within which exists a city-state reliant on technology and advanced engineering in a world depending on the supernatural. Deep in the heart of Garund, across the Shattered Range mountains, ancient ruins of unknown origin rise out of the wild, wholly uncivilized jungles. Scattered throughout the mountains surrounding the vast jungles of the Mwangi Expanse lie the ruins of once-miraculous flying cities of the Shory, long-since crashed into the rocky slopes where they now rest.
Sources: Pathfinder Chronicles Campaign Setting