A shop in Marche Serpette. [Photo/Agencies]

Also in the courtyard, Mademoiselle Steinitz's industrial warehouse mixes rare furniture, fantastical sculptures, contemporary photography and formal gowns. On a recent visit, a Viennese Arts and Crafts couch with two armchairs and two side chairs was 53,000 euros; a one-of-a-kind 1910 butterfly desk and chairs by the Belle poque fashion designer Paul Poiret cost 300,000 euros.

Nearby, three small early-20th-century houses on Rue Paul Bert are musts for lookers who may not be buyers. Un Singe en Hiver, covered with wisteria and ivy at No 6, features an inner courtyard with old stone crockery, a stone ostrich and antlers in a bowl. Sylvain Seron, who owns the space with his wife, Sylvie, will be eager to explain the history of the objects, including the construction of long metal tables from 19th-century industrial water tanks.

Up a stone staircase at La Petite Maison at No 10, Franois Casal also loves conversation, so much so that if you stay long enough he may offer you a glass of Champagne in a heavy crystal goblet. Ask him about the zinc-topped, marble-based bar with inlaid mother-of-pearl at the entrance.

My least favorite shop of the trio is Colonial Concept at No 8, although it is a taxidermist's delight, with more than a dozen stuffed peacocks, zebra heads, a stuffed leopard and a stuffed lion lying on its side; 4,500 euros will buy you a bearskin rug. Feather headdresses, white corals, polished fossils, a partial giraffe, assorted skulls, lamps made of ostrich eggs - all make it difficult for the environmentally correct visitor to embrace. Photographs are forbidden; the chilly welcome makes you wonder whether it wants customers at all.

St.-Ouen has become a better bad place to eat. For a snack or light lunch, La Buvette des Tartes Kluger in what was once a brick factory in the Habitat courtyard offers Kluger's wide assortment of homemade sweet and savory pies; lunch can be eaten on picnic tables outside.

Since 2012, there is also Ma Cocotte, a high-ceilinged, two-level brasserie designed by Philippe Starck. With several small dining rooms and two large terraces, it screams new, a contrast to the flea market's warrens of alleys. Without sufficient insulation, it also screams loud. The restaurant, which offers everything from caviar and foie gras to cheeseburgers and fish and chips, is open evenings during the week, even when the flea market is closed.

There are also the old-timers, like Caf Paul Bert for a reliable steak frites on Rue Paul Bert, and Le P'tit Landais on Rue des Rosiers for a slab of foie gras and green salad. A two-course lunch for two with wine at either place will cost around 35 euros, one of the best bargains at St.-Ouen.

In the past two years, about 50 shops have opened in Paul-Bert-Serpette, many by younger dealers. Mid-20th-century furniture, lighting and decorative arts in modern, unadorned spaces are popular, trendy and pricey.

Last spring, the Parisian media magnate Jean-Cyrille Boutmy bought Paul-Bert-Serpette. He has already implemented measures to guarantee the authenticity of the market's objects and is planning to spruce up the site.

Cyril Aouizerate, one of the founders of the Mama Shelter hotel in Belleville, in the 20th Arrondissement, is investing 40 million euros in a hotel that will open at St.-Ouen in 2016. To be called M.O.B., the 350-room hotel will include a cultural center with a bookstore, meditation rooms, an open-air movie theater and a vegetarian restaurant serving organic, local produce.

For visitors who want to shop as well as look, all is not lost. Here is a rundown of some of my affordable favorites (or at least where good value can be found).