I don't have a scanworthy map drawn up yet, so instead I'm going to be doing a bit of textual description of places. This is as much a process to get my thoughts in order as it is to potentially inform players, I guess. Still need a world name and a bunch of place names.
There are two main seas; the Inner and the Outer. The Inner is long and narrow, running north-south, and its coasts are the primary region of human settlement. The climate is wet and cold in the north, hot and dry in the south, and pleasant in between. At its southernmost extent, the Inner Sea meets the Outer Sea at the Straits of Dardantus, which take their name from the city which is built there. The city of Dardantus is a hub of trade and culture, home to the Great Bazaar and many temples, including extensive complexes of both the Harmakhans and the Ashtari. Anything which can be bought or sold is available, including magic items, Thrassian mercenaries, war galleys, exotic animals, spices, and slaves. Who or what rules Dardantus is unclear; it is known only that missives sealed in distinctive purple wax sometimes appear mysteriously, and kingdoms rise and fall upon their content. Rumor and speculation suggest demons, undead, and worse, but the common belief is that a cabal of merchant-wizards is more likely.
As a result of the lack of clear rulership, law in Dardantus is a murky business. There are magistrates operating under the authority of the seal, whose purpose is to keep commerce running smoothly. In practice, they tend to pursue only crimes against particularly wealthy merchants, and those involving destruction of large amounts of property. Corruption is exceedingly common, and bribes or small gifts are part of daily business. Justice for small crimes is, by and large, just another commodity in Dardantus to be bought, sold, and haggled over. All manner of unsavory agents are used to carry out vendettas, including the Harmakhan assassins, mercenaries, and adventurers. A number of secret societies and guilds of thieves wage a continuous proxy war; adventurers who become unknowingly embroiled in it will soon find their lives made quite interesting.
Dardantus entered human hands during the Zaharan War, when the Sorosi took the Zaharan city of Darad-Knar, upon whose ruins Dardantus was build. The Dardanians declared independence shortly thereafter, and despite their naval power the Sorosi have been unable to retake the city ever since. The fact that previous Sorosi efforts have been foiled by unfortunate accidents and freak storms is often used to lend credence to the notion that a supernatural being rules Dardantus, but wiser heads attribute the accidents at least to covert operatives. While unable to retake the city, the Sorosi pirates are known to favor ships flying Dardanian colors, and as a result Dardantus maintains almost no merchant marine of its own, instead preferring to charge others for the service of using the straits.
As a people, the Dardanians maintain much of the flamboyance of their Sorosi origins, though their tastes have been altered by their constant exposure to cultures from across the Outer Sea. They enjoy spicy food, dark wines, brightly colored clothes, intrigue, bloodsport, and other 'exciting' diversions. A grand arena caters to these latter tastes, as well as numerous smaller rings across the city. Monsters are in high demand, and many a beast-hunter from the Shieldlands to the west seeks to bag an owlbear or basilisk for sale to the arenas. These arenas also host races, duels (which in Dardantus are often by proxies or champions of both parties, in contravention to Sorosi dueling policy), and the annual Tournament Arcane, which brings an influx of mages to Dardantus in the early spring. The other great yearly celebration is the Festival of Masks, held in the fall, which is a confusing and often destructive mix of revelry and secret society activity.
Of the other cultures of the Inner Sea, the Shieldlanders, Urdukhar, and Sorosi are all common sights in Dardantus as merchants, priests, and sailors. Myrmidians in Dardantus are typically mercenaries in the employ of wealthy merchants, while the Talasi are very rare except during the season of the Tournament, which they often win. It is unheard of for the Skanuks to raid this far south, and various Skanuk chieftains are on record as not believing so large a city possible. The Sajuk horselords gave up on trying to sack the city ages ago due to logistic difficulties, but individual Sajuk are not uncommon in the employ of caravans as drovers or guides. The sandstone dwarves of the eastern mountains maintain something of a ghetto in Dardantus, as it is a common destination for their caravans and their works are held in high esteem, though the granite dwarves of the west are much rarer. Dardantus hosts the greatest proportion of Zaharans in any Inner Sea state, though there is still much prejudice against them and they tend to keep to themselves. When someone other than a Talasi wins the Tournament, it is typically a Zaharan.
Of the Outer Sea cultures, the elves are the relatively common compared to other parts of the Inner Sea. Many elves in Dardantus are believed to be agents of the Jade Throne, and often rightly so. They play well in the intrigues of the city, but have yet to win any significant control from its mysterious masters. Merchants from the island state of Volar are common as well, being a fellow Sorosi successor state, and they bear with them spices, slaves, and tales from the other cultures of the outer rim. The lizardmen of Thrassia are most common as slaves and gladiators, though a few merchants are known to employ them as terrifyingly savage bodyguards. Natives of the Crawling Isles are not uncommon, often coming in on Volari merchant vessels, but are also often slaves. The obsidian dwarves are highly valued as slaves for their rarity on account of their insular and warlike nature.
In short: In location, Byzantium meets Gibraltar. In spirit, not unlike Mos Eisley.