The Old is the Last Continent, on the Last World on the Last Plane,in the Last Universe. To the North is the Ash Sea (A desert of sorts) and to the South is The Great Salt Sea.To the East is the Brier Patch and to the West is the country-sized Morgue. Surrounding the entire place is the Corpse Sea.At the very center of it all is The City's Mesa.
The Last City that mankind will ever build is nothing special. Sure it has a few marvels based on found magic of lost ages but overall it a rather boring place, filled with the decadence of mankind final hour. The familier fantsy races have all been long forgotten but a few odd non human "ducks" remain, these are the Scarecrows and Raven-folk.
The Scarecrows are the bi-product of evil magic . Used to serve as sargents for evil humanoids, a few have developed non- evil tendencys, but still survive by violence.
The Last City should be a place of fallen splendor and forgotten wonder. The populace lives in the shadow of machina and spellcraft that they no longer understand, and can no longer replicate, or even repair as it fails. As such, the people are decadent, but they don't know many of the things that they do. They use spells, possibly more for the side effects than the actual intent. Magic items can be common, but powerful, with more mundane magic items long since depleted. Sort of like the end of a fantasy video game where the items section is full of epic and legendary gear, but none of it is used because things like mega-elixirs cannot be replaced. Melnibone of Elric fame would be a good example, as well as Erikson's Malazan series. High magic, high power, but rednecks playing with the toys of the gods.
I don't understand the relevance of the raven-folk, but sure. They need a section of the City, the Rook, where they gather, a massive black tower, the tower of ravens, etc.
Scarecrows = light golems (light as in not heavy, not the element of light), made of non-durable materials.
The huge mesa in the center of the Old, serves as home to the vast majority of the sapients of the Stolen World
The center of continental plates are called Cratons, with the Australian Craton being one of the oldest places on the surface of the planet, along with the South African craton, both being billions of years old. I think a craton, which can be hundreds of miles across, can be the core of the last continent. A badland, where the fertile soil has been washed away leaving behind salt pans, broken badlands, and things like the yardangs of Saharan Africa, or the Devil's Playground in the Southwest (where all the old westerns were filmed). Lots of wind eroded stone, and places where things can grow are few and far between.
There are going to be oases in the Craton, places where the soil has been protected, or walled in with magic, where lush gardens grow, full of exotic plants and animals, but on the other side of the barriers, there are only ruins, scrub, and the hardiest of animals. Architecturally we can have fun here, because there are plenty of old blasted locales you can crib from as needed: Krypton, Vulcan, and Gallifrey all come to mind. Litter the craton with the corpses of cities, some very well picked over, some haunted, some the domains of nomads, and some the lairs of horrible monsters drawn forth with ancient magic, but trapped inside their crumbling cages
The Ash Sea
On any other world The ash Sea is the kinda place no one would visit but here it is the main food source of The City. Large Ships sail the ash , "fishing" for Crabs and visiting the few cities that are above the 1/4 mile deep ash.
A very ocean like ecology has formed in ash with versions of turtles sharks and sea scorpions just to name a few
Nice, plenty of room for exotic monsters like sandworms, and sand dragons, and all of that.
more to come, wife just got home
The Brier Patch
Formed from magicly altered roses, The Brier Patch fills one quarter of the content. In some places 20 or 30 feet thick, movement though it is extremely difficult and always painful thorns in every step you take.
The Magic Forest, a perfect locale, the last forest, made of the hardiest and toughest of plants, altered by magic, and able to survive in the harsh climate of the last age. There isn't too much for me to add, the magic forest is the magic forest. It isn't a refuge, it's teeming with scrub goblins and hoary fungal trolls, and it is a hungry place, eager to drain you of magic, will, blood, and life, to feed itself. But, the most lovely flowers bloom there.
The Great Salt Sea
The name is a misnomer it is not salt that pollutes the sea but the by product if generations of magical waste from poorly prepared wizards and there underlings.
The Great Salt Sea, the last ocean, that all the final rivers drain into. It's dirty, both from centuries of magical waste, and tens of centuries of mundane garbage. There are many islands, places of horror, out in the Salt sea, where that magical waste washed up and concentrated, places where the rocks are alive, but animals are not. Plenty of room for curses, ships of the dead and the damned, and stuff like Captain Penguin's Mountain of Boats submission.
Generations have filled this area with the corpses of loved ones, so much so as the place is nearly one tremendously huge necropolis.
Necropolis, Terra Mortuis, the land of the dead, for now the dead outnumber the living as they never have, and as these are the end times, as they never will again. It isn't a single city, it's a whole region of them, like the Upper Nile, where Karnak and Abu Simbel are filled with monuments and great tombs, and the vaults of the royal and imperial dead. Hundreds of empires have built Terra Mortuis, and it's great capital, Necropolis, the city of the dead Kings.
The undead rule some of the these tomb cities, some are simply haunted. Is there a rumor that one day that the greatest and most terrible of the Tomb Kings will rise, and unit the armies of the dead, creating a host so vast that the cloud it raises on the march will blot out the sun, and the stench of their approach will be as devastating as a terrible plague? Plenty of room to make more than one city of the dead, lots of prophecies, places to loot, and shittons of deadites to hunt and return to death