If you enjoy www.victorianlondon.org why not ...
Victorian London - Thames - Tunnels - Tower Subway
As I was thinking of these things I disappeared from the world indeed, going down a lighted spiral staircase which buries itself in the earth on the right bank of the Thames, opposite the Tower. I went down and down between two dingy walls until I found myself at the round opening of the gigantic iron tube, which seems to undulate like a great intestine in the enormous belly of the river. The inside of this tube presents the appearance of a subterranean corridor, of which the end is invisible. It is lighted by a row of lights as far as you can see, which shed a veiled light, like sepulchral lamps; the atmosphere is foggy; you go along considerable stretches without meeting a soul; the walls sweat like those of an aqueduct; the floor moves under your feet like the deck of a vessel; the steps and voices of the people coming the other way give forth a cavernous sound, and are heard before you see the people, and they at a distance seem like great shadows; there is, in short, a sort of something mysterious, which without alarming causes in your heart a vague sense of disquiet. When then you have reached the middle and no longer see the end in either direction, and feel the silence of a catacomb, and know not how much farther you must go, and reflect that in the water beneath, in the obscure depths of the river, is where suicides meet death, and that over your head vessels are passing, and that if a crack should open in the wall you would not even have the time to recommend your soul to God, in that moment how lovely seems the sun !
I believe I had come a good part of a mile when I reached the opposite opening on the left bank of the Thames; I went up a staircase, the mate of the other, and came out in front of the Tower of London.
Edmondo de Amicis Jottings about London (trans), 1883
Tower Subway.—A curious feat of engineering skill, in the shape of an iron tube seven feet in diameter driven through the bed of the Thames between Great Tower-hill and Vine-street. The original intention was to have passengers drawn backwards and forwards in a small tram omnibus. This, however, was found unremunerative, and the rails having been taken up the tunnel has since been open as a footway. Unfortunately, however, after subtracting from its diameter the amount necessary to afford a sufficient width of platform, there is not much head-room left, and it is not advisable for any but the very briefest of Her Majesty’s lieges to attempt the passage in high-heeled boots, or with a hat to which he attaches any particular value. It has, however, one admirable quality, that of having cost remarkably little in construction. NEAREST Railway Stations, Aldgate (Metrop.) and Cannon-street (S.E.); Omnibus Routes, Aldgate High-street and Fenchurch-street; Cab Rank, Great Tower-street.
Charles Dickens (Jr.), Dickens's Dictionary of London, 1879
John Fletcher Porter, London Pictorially Described, [1890]