Unfortunately, the map we dispose of is no earlier than the 17th Century. It is very approximate, the camp of Cesar is shown to be west of Arugueloura, but it is in fact south. And no pathway corresponds in the near area to à full westward or 7 o'clock direction. However, the modern roads probably overlap the old pathways. The best fit would be D213 on the previous map.

Althought it is not visible on the map, the city of Mirande is just a little up north-east of the Cesar Fortification. Mirande is probably situated on an itinary implied by the seer that leads to a mysterious ancient place. It is referred to in two instances, one having to do with THE great earthquake, and the other in what appears to be a nuclear conflict:

1.46
Very near Auch, Lectoure and Mirande"
a great fire will fall from the sky for three nights.
The cause will appear both stupefying and marvelous;
shortly afterwards there will be an earthquake.

8.2
Condom and Auch and around Mirande,
I see fire from the sky which encompasses them.
Sun and Mars conjoined in Leo, then at Marmande,
lightning, great hail, a wall falls into the Garonne

In turn 1.46 may link to 2.52.