Geography of Fallen London's Surroundings

What exactly do we know about The Stolen River? Seeing that it leads westward it’s probably one of the five rivers of hell. Since the lake Avernus in Sunless Sea is the classical entrance to the Roman underworld we can also assume that the Hell in the Failbetter Games universe shares at least some geographical similarities to Hades.

Does anyone have any ideas as to how the Bazaar managed to steal The Fourth City from Central Asia and then pull down the City of London on the exact same spot? Is the Unterzee tethered in place beneath real world landmarks or does it move freely? If the Unterzee moves than how is any sustained connection to the surface, such as the Cumean Canal, possible?

I’d like to add to the map from Sunless Sea and try to fill in some of the unknown areas inland from the Unterzee.

I was under the impression the stolen river was the Thames. A bit less exciting than your theories, but I am fairly certain the text states this in some places.
The Bazaar has a way to move itself, so it probably did move to steal London. I suppose it can just stop moving after it stole a city, allowing permanent structures to be built.

The Stolen River is definitely the Thames. Hence the name – it was stolen with the rest of London.

The Unterzee doesn’t “move”, exactly; the islands in it reshuffle periodically. Hell is directly west of London, and the coastlines (which the Cumaean Canal is part of) do not move. The Travertine Spiral is the only other connection to the Surface and that is farther inland to the west.

What I WOULD point out as strange, and probably a baseline for anyone who wanted to delineate the barriers, would be Aestival, which appears to be completely immune to the sunrise/sunset cycle.

But does the stolen river have the same source as the Thames? I Imagine it has a different source from it’s real world counterpart. If Fallen London is anywhere near the source of the Thames then that means that it’s roughly 1000 miles from the Cumean Canal which comes out near Naples. All indications point to the Cumean Canal being closer

While it’s course through London Might be similar to the Thames that doesn’t mean that the rest of the river is identical.

Also what do we know about the travertine spiral?
edited by IgnatuStone on 6/19/2015

Isn’t the Cumean Canal pretty long?

The Cumean Canal Travels 1 mile upwards using locks. If it was completely linear I estimate that it would be 40 miles in length. I’m using the measurements from the Panama Canal Locks. However I suspect it spirals.