The Subway series is the deepest level presently known in Steinbrückenhöhle. It is in a steeply sloping bedding plane at an average altitude of around 1400m. Access is from the Subsoil level via the Four Pitches of the Apocalypse.
This pitch series starts at a chamberette in a side passage in the Fat Worm Blows a Sparky area of the Subsoil level. A wide Y-hang across the passage protects a short muddy ramp, which is followed by a traverse to the left across a wide ledge to the first main pitch. I can't remember anything about this pitch, but the next pitch is somewhat damp, and lands at a traverse along the left-hand side of a slot until it opens out wide enough to descend. This third pitch is 21m long and lands at a small round ledge. Here the water disappears down a narrow round hole to one side [XXX Is this not a QM? i can't remember. Perhaps it would be too small to get a body through. Certainly a C-- grade lead.] while the main shaft continues straight ahead from a Y-hang on the right-hand wall (needing 2 maillons to avoid a marginal rub) and an immediate deviation. The next pitch is a spacious 34m, with a deviation part-way down. Shortly beneath this a swing through a window leads to the main Subway series, while continuing down the pitch leads to Mornington Crescent. It should be noted that in wet weather the lower pitches become very drippy and the deviations are essential to keep you out of the water.
The final Pitch of the Apocalypse lands in a chamber floored with boulders, with one huge block in the centre. Around 5m off the ground, it is possible to swing off onto a ledge, where a hole in the wall reveals a sporting passage which spirals down steeply in a corkscrew pattern, passing several short climbs and a tight bend (requiring SRT kit removal, at least if you're as fat as Dave). Beyond this the passage appears to close down, although there are one or two unexplored side branches [C2005-204-59 C], and the passage has not been surveyed.
The continuation of the pitch series is Mornington Crescent [NIAL] [C2005-204-60 B] [C2005-204-61 X], which ends at a too-tight pitch-head 60m further down. It appears that in wet weather this pitch head sumps and that the water partially fills the shaft.
Swinging through the window from the Fourth Pitch of the Apocalypse, a short drop belayed off a spike lands on a wide ledge. Traversing to the right leads to a steep upward slope, at the top of which a passage leads right and left; to the left is [C2005-204-50 C] and to the right is [C2005-204-49 B] (the latter has an 11-second rattle). Traversing leftwards reaches a short pitch into the spacious, boulder-floored Turnstile Chamber. An aven enters to one side [C2005-204-51 X] while continuing on leads to a funnel-shaped hole in the floor. This is rigged with a Y-hang from a pillar and a spit, and a deviation to the other wall, but this requires some athletic manouvres to pass. The pitch is only 5m deep and lands in another large chamber. (The pitch can be bypassed by a climb down through the boulders, but this is not recommended, as the boulders are not especially stable.). [XXX This is as far as I ever went and everything else here is solely based on the survey! XXX]
In this next chamber which I propose be called The Platform, a climb-up the right-hand wall leads to an unpushed crawl [C2005-204-52 A], while straight on leads down a couple of minor pitches past another passage on the right [C2005-204-53 B] to a 9m pitch. This lands in a wide passage, The Tube. There is a hole in the floor [C2005-204-54 C] while the passage continues both north and south.
Heading southwards from the pitch into The Tube, the passage passes under an aven [C2005-204-55 X] soon reaches a complex junction, St. Pancras. The main passage loops round on itself, passing various small passages [C2005-204-56 C] [C2005-204-57 C] [C2005-204-58 C]. To the left is a pitch, Pig's Ear Pitch, which can be either descended or traversed round. Traversing across leads to an upward-sloping passage, Docklands Light Railway. At the top of this is a pitch [C2005-204-26 A], with a passage visible across the pitch-head [C2005-204-27 B]. The main passage continues ahead; exploration was halted by a pool of water, which could be traversed over [C2005-204-28 A].
Descending Pig's Ear Pitch from St. Pancras leads to the Picadilly Line, a very wide, boulder-floored passage. This slopes downward, passing an aven [C2005-204-25 X]. Beyond this is a junction, with another aven [C2005-204-24 X] above it. On the left is a narrower passage leading to Green Park, while ahead Picadilly Line continues, still sloping downwards. After around 50m it narrows and swings to the left, passing a passage [C2005-204-23 B] on the left. This final section carries a trickle of water in a trench in the floor. At the end of the passage this disappears down a hole in the floor [C2005-204-22 B], beyond which is a 10m pitch, Dog's Dinner, with very poor quality rock. This lands in a large chamber, Hounslow, with a boulder floor. Above is an aven [C2005-204-20 X]. In the floor are two more holes. The smaller is [C2005-204-21 B], while the larger leads to a 24m pitch, Dog's Bollocks. The water rejoins part-way down, and at the bottom is a sump, at a depth of 490m from 204e.
From the junction in Picadilly Line, an upward-sloping side passage leads off. This passes a 2m climb to a juction, Green Park. Straight ahead the passage continues for a few metres between large mud banks, but the main route doubles back over itself and emerges in another passage, Jubilee Line Extension, which runs for around 50m parallel to and more or less directly above the Picadilly Line. Holes in the floor [C2005-204-31 B] [C2005-204-83 C] presumably connect. At the end, the passage forks, with walking-size passage continuing in both directions [C2005-204-29 A] [C2005-204-30 B].