About that exploration: It yielded the kind of unexpected discoveries — virtually all of them easily accessible by Métro or tram for those uninterested in a 35-mile ramble — that I had all but given up hope of finding in hyper-gentrified tourist magnets like Paris. To cite just a few (a handful of which I owe to the Enlarge Your Paris guys, the others to happenstance): I hiked in a forest, had a close encounter with the actual embalmed heart of Louis XVII and listened to a cumbia band in an immense former marble factory alongside French hipsters drinking American I.P.A.s. I gazed in awe at some of the most ugly-beautiful Brutalist buildings I’d ever seen, ate an exquisitely poached filet of whiting with spring peas at a serene restaurant where the bread comes in a miniature burlap sack, and ambled around an empty museum filled with sleek 1930s furniture that, in the absence of any other visitors or even (as far as I could tell) a guard, I found exceedingly hard not to sit on.

My first mistake: Wine at lunch. (Soon repeated.)

Here’s one thing to know before trying to walk the perimeter of Paris in a week: The city and its pleasures will no doubt conspire against you. On my very first day, after a morning spent pushing north from my hotel along the Boulevard Soult, past a locksmith business, a car-insurance agency, a shoe repair shop and other emblems of everyday Parisian life, and after a foray into the unlovely suburb of Bagnolet, I found myself very badly in need of lunch. So I plunged a few blocks into the city and installed myself at an outdoor table at a busy cafe in the 19th arrondissement called La Pelouse. One 11-euro plat du jour, a carafe of chilled Brouilly and a crème caramel later, I found the idea of rising to my feet — much less continuing my trek — less than appealing, especially with the ever-entertaining human pageant playing out before me on this busy corner in Belleville. After that, I made a promise to myself to exclude wine from lunch for the remainder of the week. (It’s a promise I would fail to keep.)

If a single observation stands out from that first, long day’s walk, which ended just before sunset in Pantin, alongside the recently restored and promenade-lined Canal de l’Ourcq — a site Mr. Delourme had referred to more than once as “the Champs-Élysées of Le Grand Paris” — it’s that Paris’s edge areas have for the past century served as a vast laboratory for bold and occasionally bonkers architecture.

Beyond the Boulevards des Maréchaux, the inner ring of surface streets that mark the limits of the Paris most visitors know, the uniform ranks of Haussman-era buildings give way to a crazy-quilt of styles and eras, from the orange-brick HBMs (“Habitations à Bon Marché”) erected near the city limits in the 1920s and ’30s as affordable dwellings — no longer very affordable at all — to their much-maligned successors, the megalithic postwar housing projects known as HLMs (“Habitations à Loyer Modéré”). The latter represent the most visible if not the most loved aesthetic legacy of the architect and urban planner Le Corbusier, whose Leviathan visions of collective living haunt the outer areas of Paris like pre-cast-concrete ghosts. (Speaking of Le Corbusier, on the fourth day of my walk I would happen upon his home and studio in a western suburb; the building is perfectly human-scale and pleasant. Go figure.)