The series is commonly labeled as steampunk, based on frequent appearances of anachronistic technology, storytelling and visual traditions of the scientific romance era,[1]: 118–119  and its retrofuturist parallel world setting of imagined cities and cultures inspired by Jules Verne's literary depiction of Europe in the late 19th century.

[1]: 143  The Obscure Cities has no unifying narrative, instead telling a series of unrelated stories, which have spanned genres such as pseudo-documentary, travel literature, psychological drama, and political satire.

Meanwhile, his older brother, Luc, introduced the young François to Franco-Belgian bandes dessinées, with René Goscinny, Morris, and André Franquin among his early favorites.

[1]: 65 Schuiten's artstyle utilizes realistic line art, emphasizing outlines and flat colours according to the Belgian ligne claire tradition, but also incorporating tonal techniques akin to engraving, with heavy use of hatching and cross-hatching.

[1]: 11  His detailed, multi-step processes incorporate sketches, storyboards, and extensive visual research, which suited À Suivre's serialization schedule.

Influential ideas cited by Peeters include Deleuze and Guattari's concept of the rhizome, Jacques Lacan's theories based on Borromean rings, and Sigmund Freud's description of the uncanny.

[1]: 145 Various commentators, as well as Schuiten himself, have identified visual and theme influences in Les Cités obscures from as diverse works as those by Verne, Winsor McCay, Franz Kafka, René Magritte, Giovanni Battista Piranesi, Victor Horta, Henry Fuseli, and Jean-Léon Gérôme.

The text is heavily annotated in emotional handwriting by Eugen Robick, the main character of La fièvre d'Urbicande who is now locked up in Brüsel's Sixth Hospice, the city's mental asylum.

[3] The volume Voyages en Utopie (2000) presents the ongoing and completed work carried on by these two authors, in parallel with the Cités obscures series.

The world (or "continent", according to the authors) of the Cités obscures forms a disparate grouping of cities located on a "counter-Earth", which is invisible from our Earth because it is situated exactly opposite it on the other side of the Sun.

[5]: 5  In Le Guide des Cités, Schuiten and Peeters directly incorporate assertions and quotes from this correspondence, even where the claims contradict published material.

In the Obscure Cities series, at times characters refer to the vanished city-state of Taxandria which was accidentally removed from the planet during a failed scientific experiment.

A setting of La fièvre d'Urbicande appears in the 2012 Canadian science fiction movie Mars et Avril by Martin Villeneuve, based on the graphic novels of the same name.

As a matter of fact, François Schuiten agreed to have a 3D model made out of his futuristic auditorium, for a scene taking place inside the Temple of Cosmologists.

After having colorfully satirized the destructive modernizing fad of Bruxellisation in the Les Cités obscures album Brüsel in 1992, Schuiten and Peeters convinced the community of Schuiten's childhood district Schaerbeek to acquire one of the last remaining buildings in Brussels built by Art Nouveau architect Horta, La maison Autrique, and in 1999 opened a permanent pseudo-documentary exhibition inside, regarding the Obscure Cities, 19th century Art Nouveau Brussels, and detailing its ongoing Bruxellisation destruction during the 20th century, tying in with aforementioned conspiracy theories whereby Bruxellisation is supposed to be an attempt by the authorities to destroy a number of Obscure Passages situated in Brussels.

Also, their latest Les Cités obscures two-part graphic novel album La Théorie du grain de sable (2007; 2008) deals with the maison Autrique.

[8] The album Le retour du capitaine Nemo, published in October 2023, depicts the "Nauti-pouple", a part-animal imaginary vehicle inspired by Jules Verne's Nautilus.

In a multi-year collaboration with French sculptor Pierre Matter, Schuiten co-designed the Nauti-pouple as a 6-metre-tall public sculpture, which will be displayed in Brussels, followed by permanent installation at Amiens station in 2025 to commemorate the city's connections to Verne.

[10] The full series is available in French and Dutch from Casterman; in German, Spanish, Polish (Manzoku and Scream Comics) and Portuguese by local publishing houses; in francophone Canada by Flammarion; and in Japanese in four collected volumes by Shogakukan-Shueisha Productions.