This is the most deliberate walk in Paris: a single straight line laid out over three centuries, from Napoleon's arch to the king's palace, designed to be processed along. Do it on foot, in the afternoon, and you feel the city's whole sense of itself.
Start under the Arc de Triomphe — through the underpass, never across the roundabout. The rooftop view down the twelve avenues is worth the climb, but the arch alone is enough to begin. Walk down the leafy upper Champs-Élysées, keeping to the garden end where the chestnut trees still stand, to the Grand Palais and Petit Palais. The Petit Palais is free and its courtyard garden is the secret pause of the route.
Then Place de la Concorde, the obelisk at its centre, where the axis snaps into a straight line in both directions. Cross into the Jardin des Tuileries and the road noise drops away — gravel, ponds, the famous green chairs. Pull one to the water.
The garden ends at the Louvre pyramid, and so does the axis. The Métro is right there.