Follow the wall of Philip Augustus and you walk within the Paris of the 12th century. There are still visible remnants of the ancient wall and towers, somehow miraculously preserved. Others are less obvious like the orientation of a street, the shape of a building or even the direction of chimneys.
In 1190, before Philip Augustus went on the third crusade, he ordered the construction of a wall around the city to protect Paris against
the threat of Anglo-Norman invaders.
It was first built on the right bank around the merchant area. Starting in front of today Ile Saint-Louis, it included the lower part of the Marais district and the Central Market and was reinforced by the Louvre fortress.
Built outside the wall, the Louvre was defending a weak point against threat from the west.
The wall was built later on the left bank once the king was back from the crusade. Starting opposite to the Louvre fortress,
it included the area of Saint-Germain and the hill of Sainte-Geneviève and was ending in front of the Ile Saint-Louis.
Plan of Paris by Braun
About 9 metres high, 5 kilometres long and 3 metres thick, it was protected by 77 circular towers. A dozen of large gates opened onto the major roads of the kingdom. At that time, the city was also including many gardens and pastures essential to feed Parisians in case of siege. As the city expanded, especially on the right bank, the wall was later replaced by the new enclosure of Charles V. Gradually torn down, built over and swallowed up, some parts of the wall remained intact hidden by constructions until recent renovations.
You can do the stroll in one go if you wish. I have rather divided it into three parts, letting time to visit points of interest along the way: