The Elder and Western Continents.

In real life, the African continental plate is being subducted under the Eurasian plate, and being melted into magma. In Failbetter’s universe, it’s still being subducted, but instead of turning into magma, it’s emerging in the Neath. The African continental plate’s upper right end matches the Elder Continent pretty well, too. Of course, the Elder Continent extends farther east than the African plate. That’s where the Arabian plate comes in. It was once part of the African plate, only 25 million years ago, and the hypothesized location of the Garden of Eden. I have no clue what the Western Continent is, though. But, since, for some reason, Fallen London is underneath its original location on the surface, since you can escape with your spouse to a village in Somerset. Here’s the link.

That leads me to believe that the Neath is actually tilted a bit, or the Sunless Sea map is less accurate in the placement of the Western Continent’s shores.

I’m not sure that the Western Continent, as you put it, is really a continent proper. In my understanding it’s more of a cave wall with outcroppings of land large enough for cities. After all, if there was an entire continent that way, The Twelve-Fifteen From Moloch Street would feature more than just tunnels and caves.

Wait, how long is the trip to hell? Let’s see what it’s under!

Does make sense, seeing as the easternmost outcroppings of the Elder Continent feature Varchas, which is definetly more arabic than african in theme.

In-lore, it’s Angkor Wat.