Plan D. Busson and V. Charlanne. Cliché
IGN Photothèque Nationale - 1999.
||The main streets
Some of Lutetia's principal roads still exist today. These are primarily cardines such as the cardo maximus rue Saint-Jacques, the cardo Boulevard Saint-Michel and the cardo rue Valette. On the right banks, there is the cardo maximus rue Saint-Martin and another cardo rue Saint-Denis.
The decumani have been almost completely erased from the present-day topography of Paris. Some of them did not exactly follow the lines of the initial grid, which shows that the Roman town planners adapted the layout of the city when necessary. Thus, the l'Ecole des Mines decumanus is roughly ten metres south of where it should be. To the north, the distance between the decumanus that is thought to have run alongside the Cluny baths, parallel to the Boulevard Saint-Germain and the decumanus of the Rue des Ecoles is not 300 but 400 Roman feet.
Adaptations of the grid system
There are also streets that run diagonal to the grid system, but that are nevertheless part of the urban plan. For example, the road formed by the Rue de la Sorbonne and the Rue Victor-Cousin ran along the eastern side of the Cluny baths-which was 300 Roman feet long-and ended at the entrance to the forum. However, the entrance was in relation to the long side of the monument, and the road was adapted to this.
Another example of this is the via transversa that started from the city's zero point and joined the Melun road. The line of this road is a perfect diagonal of a rectangle measuring two and a half units by three units. This road-most likely an important one, since it linked the capital of the Parisii with Italy via Melun and Lyon-had thus been anticipated from the beginning of the construction of the Roman city.