THE FILM WE have settled in to watch – Sans soleil, directed by one Chris.Marker, the pseudonym of world cinema's best-known invisible, his name already futuristically punctuated like myriad dots to com – was completed in 1982, but it might as well have been made a million strange days into the future ... or a thousand Saturnian nights into the past. It begins by describing a second film, also titled Sans soleil, which the narrator, reading from and commenting on letters ostensibly sent to her by a globe-trotting filmmaker, informs us will never be made, a film in which the images we have already begun watching – bits of gorgeously colored documentary footage of far-off places and the faces of people staring back at the camera as boldly as it stares at them – tell yet another sort of story, part science fiction, part half-remembered fact. The two films – made, unmade – intertwine in a single Möbius strip, a film whose title means "sunless" that is everywhere about the qualities of sunlight (on people, on film stock) – a dream, a travelogue, a horror movie, an epic poem, a letter from the future, a list of things that quicken the heart, and a remembrance of things past.

The narrator's voice (a hypnotic flat line pierced by occasional thorns of wry humor) offers one poetic counterpoint after another to the already densely associative flow of sounds and images at work. Icelandic children with seemingly irradiated blond hair negotiate for Earth space with a relentless volcano while a granite dog awaits the return of his master, long dead. Revolutionary moments from remote African ports of call unfurl in flurries of guerrilla warfare and sudden death, and a tower of Japanese video babble takes a Buñuelian razor blade to the irises of history, using a now-primitive image synthesizer to slice open news footage of modern samurai. Dead pandas and dead presidents are resurrected as robots in Shinjuku department stores while an ancient astronaut roams the streets of San Francisco, excavating the remains of a planet once known as Vertigo. January light on some Tokyo subway station's stairs somehow joins with the image of a pair of canines nipping at one another and darting through foamy sea break on the other side of the world – and finally it seems as if the entire film is Proust's madeleine reimagined as a dog biscuit: you could watch Sans soleil backward or forward, or overundersidewaysdown for that matter. Everything is attached to everything, and each cut from image to image is deeper than the last.

But simply saying Sans soleil marks the apogee and outer limits of the essay film – in which images are assembled according more to themes and clusters of ideas than to personalities and narratives longer than a moment or so in duration – is a little like saying Joyce's Finnegan's Wake is a book with a lot of big words. André Bazin once suggested the term "lateral montage" to describe the way Marker layers multiplicities of meaning in his work by using reiterated and recontextualized images and narration that constantly attempts to rethink and reassociate ideas we encounter in polyrhythms throughout the film. Of course, one generation of cinéastes after another has already embraced and absorbed Sans soleil, but even as the screening of a new print at the Castro Theatre this week will give the already faithful an opportunity to revisit their shrine, it will also remind them of the way the film seems to make its viewers (and reviewers) novitiates with each new viewing: it's a film that can't simply be watched to be fully appreciated; it must be rewatched and reworked in the viewer's mind. I must have seen it 20 times in the past 20 years, but watching it again last week, I was knocked out afresh by the trippy prescience of its sound design: moaning metal in the distance behind a Tokyoscape of "pictures larger than people," computer burbles beneath percussion racket from a Cape Verdean street parade, and occasional shards of angular ambience from the Mussorgsky song cycle from which the film takes its title.

Sans soleil remains the quintessential study of postgeography – national, political, and emotional – in all of modern cinema, so much so that it's tempting to go ahead and call it The Last Documentary but for the fact that Marker, now in his 80s, is still making films. San Franciscans have always embraced Marker – a filmmaker as legendary as he is cloaked in mystery, and the subject of a massive two-part reappraisal in the pages of Film Comment this past summer – as much as he embraces the city in the Vertigo section of Sans soleil. And his films have appeared with regularity at the San Francisco International Film Festival. Magically, a viewing of Sans soleil at this particular moment even manages to extend the ping-ponging of emotional associations between the filmmaker and the city to the current-day Castro calendar, when a shot of a shopping bag bearing a caricature of Jean Gabin – in full tuxedo-and-trench-coat regalia from the recently screened Touchez pas au grisbi – turns up in a sequence regarding "Martian" dancers in Tokyo's Yoyogi Park. Such are the amazements of Sans soleil, a film that, no matter how many times you look at it, seems somehow always to be looking back at you.