#lesmis365

Disclaimer: all the labels are my best estimates based on the text and an occasional glance at street maps. I’m making no claims of Actual Research here. :p

(1)  Valjean starts off from a small side-channel under the rue de la Petit-Truanderie that connects to Montmartre sewer: there he has to decide whether to turn left (towards Seine) or take longer but safer way uphill.

"He said to himself that he was probably in the sewer des Halles; that if he were to choose the path to the left and follow the slope, he would arrive, in less than a quarter of an hour, at some mouth on the Seine between the Pont au Change and the Pont-Neuf, that is to say, he would make his appearance in broad daylight on the most densely peopled spot in Paris... He ascended the incline, and turned to the right."

Even so, he gets disoriented almost immediately, because he assumes himself to be under the rue Saint-Denis (2), which would have been easier going:

"Under the Rue Saint-Denis there is an old stone sewer which dates from Louis XIII. and which runs straight to the collecting sewer, called the Grand Sewer, with but a single elbow, on the right, on the elevation of the ancient Cour des Miracles, and a single branch, the Saint-Martin sewer, whose four arms describe a cross."

Instead he gets stuck with Montmartre sewer, which "is one of the most labyrinthine of the ancient network".

By moving away from the Seine he manages to avoid the network under Les Halles (3)

"The sewer of the markets whose geometrical plan presents the appearance of a multitude of parrots' roosts piled on top of each other" 

but there is still a risk of being confused by:

(4) "The vast sewer of the Plâtrière, a sort of Chinese puzzle, thrusting out and entangling its chaos of Ts and Zs under the Post-Office and under the rotunda of the Wheat Market, as far as the Seine, where it terminates in a Y

(5) “on his right, the curving corridor of the Rue du Cadran with its three teeth, which are also blind courts”

(6) "on his left, the branch of the Mail, complicated, almost at its inception, with a sort of fork, and proceeding from zig-zag to zig-zag until it ends in the grand crypt of the outlet of the Louvre, truncated and ramified in every direction"

(7) the blind alley of a passage of the Rue des Jeûneurs

The policemen who almost catch Valjean come out from (5):

"This patrol had just visited the curving gallery and the three blind alleys which lie beneath the Rue du Cadran. While they were passing their lantern through the depths of these blind alleys, Jean Valjean had encountered on his path the entrance to the gallery, had perceived that it was narrower than the principal passage and had not penetrated thither. He had passed on. The police, on emerging from the gallery du Cadran, had fancied that they heard the sound of footsteps in the direction of the belt sewer."

Valjean reaches the belt sewer/le grand égout about "three hours past midday":

"He was, at first, astonished at this sudden widening. He found himself, all at once, in a gallery where his outstretched hands could not reach the two walls, and beneath a vault which his head did not touch. The Grand Sewer is, in fact, eight feet wide and seven feet high.

At the point where the Montmartre sewer joins the Grand Sewer, two other subterranean galleries, that of the Rue de Provence, and that of the Abattoir, form a square. Between these four ways, a less sagacious man would have remained undecided. Jean Valjean selected the broadest, that is to say, the belt-sewer."

Valjean has to decide once again whether to go left or right, but between his own exhaustion and Marius being super nearly dead, he decides to go downhill (left). This, as Hugo points out, is just as well, since he would have had hell of a time getting out from the other end:

"It is an error to suppose that the belt-sewer has two outlets... and that it is, as its name indicates, the subterranean girdle of the Paris on the right bank. The Grand Sewer... terminates... at the foot of the knoll of Ménilmontant(9). There is no direct communication with the branch... which falls into the Seine through the Amelot sewer above the ancient Isle Louviers... If Jean Valjean had ascended the gallery he would have arrived, after a thousand efforts, and broken down with fatigue, and in an expiring condition, in the gloom, at a wall. He would have been lost.

In case of necessity, by retracing his steps a little way, and entering the passage of the Filles-du-Calvaire (10), on condition that he did not hesitate at the subterranean crossing of the Carrefour Boucherat, and by taking the corridor Saint-Louis, then the Saint-Gilles gut on the left, then turning to the right and avoiding the Saint-Sebastian gallery, he might have reached the Amelot sewer, and thence, provided that he did not go astray in the sort of F which lies under the Bastille (11), he might have attained the outlet on the Seine near the Arsenal. But in order to do this, he must have been thoroughly familiar with the enormous madrepore of the sewer in all its ramifications and in all its openings. Now, we must again insist that he knew nothing of that frightful drain which he was traversing; and had any one asked him in what he was, he would have answered: "In the night."

So Valjean goes left and walks a bit before stopping to  rest "probably" right after Madeleine branch, "probably" under Rue d'Anjou (12).

"A little beyond an affluent, which was, probably, the Madeleine branch, he halted... A passably large air-hole, probably the man-hole in the Rue d'Anjou, furnished a light that was almost vivid."