Two miles before the junction of the two rivers the Marne makes a loop to the south, in this way running parallel with the Seine for about three miles.

On the north of the Marne towards Paris lies the wood of Vincennes, and beyond the loop there are the villages of Joinville, Nogent, and Brie.

The line is defended by the forts of Vincennes and Nogent and the redoubt of La Faisanderie.

To the south, between the loop and the Seine, is the fort of Charenton; a little farther on the village of Creteil; beyond it, just outside the loop, is Montmesly, where the Prussians have heavy batteries.

On the north side of the loop is the village of Champigny, which is situated on a plateau that extends from there to Brie.