In These Strange Worlds Red, magic is possible. Humans rule, but only barely. Hundreds of different sentient races live in Red, including many whose whole metabolism is based on magic and not biochemistry.
When most people think of Red, they think of the Empire of Heinlein the Black. Heinlein's Empire encompasses an area similar in many ways to Strange World Yellow's Europe. All in all, the continent is divided into eight Heinleinic civilizations. Hoblinland, called Goria by its inhabitants, is Germany. Elfland, called Cyrenia by its inhabitants, is France. Lizardmanland, called Hiastia, is Spain and Portugal. Centaurland, called Rimardia, is Poland and western Russia. Ogreland, called Ilastia, is Italy. Vegetablemanland, called Frondia, is the Balkans and Turkey. Giantland, called Burdia, is Scandinavia. The Empire also includes three great underground and undersea civilizations: the Dwarves, Mermen, and the Panzerscorps. The landscape is dotted with many smaller lands. Heinlein's actuaries have enumerated almost 3,000 lesser races, some mere tribes of a few dozen members and some small nations. There are also some six thousand registered citizens who belong to no known race or civilization. These "one of a kind" creatures represent special constructs, remnants of extinct species, and in a few cases visitors from Strange World Blue.
Heinlein's Empire also contains civilizations that were never assimilated or are even contrary to Imperial ambitions. These include Ifrits and Ghuls, who loved in the clouds and desert wastes, tiny sprites and fairies, subterranean ghouls and dragonkind.
Not all the known world is controlled by the Empire. High Craig, the equivalent of Switzerland, remains independent. The less said of Gloriana, the equivalent of Ireland, the better. To the south, Africa is known as the Parchland Wastes. To the east are the powerful but mysterious Oriental kingdoms of Raj (India), Shogun (China and Japan), and Rurik (Siberia). To the west, across the vast Sea of Sargasso is the double continent of Atlantis (the Americas).
Heinlein carefully controls entry into his empire.Most Doors from the Red tunnel are wedged shut by his team of "Mallets." Entry is still indirectly possible through High Craig, the Parchland Wastes, and elsewhere, but most of the people who make it to the tunnels do so with the Empire's permission.
Then there is Erie. The magical equivalent of Ireland has more Doors per area than any other known location in These Strange World Red. For most people, it's "Look but don't enter. The island is sealed off by magical and mundane means much more sophisticated than Heinlien's wedges.
Most of the Doors closest to Nexus City open to Erie or the Empire and can't normally be opened. Although there are exceptions, Doors to High Craig and the Parchland Wastes are a longer walk. Door to Atlantis, Raj, or Shogun are much further away.