A girl with piercing blue eyes walks into an elevator. She gets shot. A hooker with long golden hair writhes seductively on a bed. She gets her soul eaten. Welcome to just another day in Sin City, where everything that’s beautiful dies, along with everything else. The newest film in Robert Rodriguez’s arsenal of digital marvels — the “Spy Kids” series were his, not to mention 1995’s “Desperado” — “Sin City” explores man’s greatest fear at its most seductive, tapping into our basest instincts with an addictive mixture of guns, leather and noir. Rodriguez has no qualms about fetishizing death, and although killing never looked so sexy, “City” often feels more like a snuff film than art. But screenwriter and co-director Frank Miller has a knack for delivering trashy dialogue that is smart and punchy, adding legitimacy to the bloodthirsty fun.

At its best — the first hour and 15 minutes to be exact — “Sin City” is a lusciously filmed guilty pleasure. At its worst it may be the downfall of meaningful cinema. (Either way, it’s a good movie to hit up with a few drunken friends.)

Like the equally-violent “Pulp Fiction,” the film’s plot is divided up into three vignettes, involving an intertwining cast of shady regulars at a back-alley bar. The first story bounds after the man-beast Marv (a barely recognizable Mickey Rourke) as he gleefully tears flesh from everybody he can get his hands on, while throwing out one-liners worthy of “The Evil Dead.” Holding up the middle is a fleshy tale of the world-weary Dwight (Clive Owen), and a harem’s-worth of whores. Chief among them is Gail (Rosario Dawson), whose mohawk is almost as big as her mouth. The weakest story of the bunch trails Hartigan (Bruce Willis), who saves a young girl named Nancy from a pedophile, only to end up rotting in prison for years. By the time he’s released, sweet little Nancy Callahan has filled out, taking on the form, and blowing hair, of Jessica Alba.

In bringing Frank Miller’s comic books to life, Rodriguez creates a world that certainly looks drawn. Most of “Sin City” is shot in the grimy metallic gray of pencil-work — and all too brief snatches of brilliant color only serve the purpose of accenting the dreariness. Perhaps due to the limitations of green-screen filmmaking, Rodriguez disproportionately lingers on intense closeups, which would create an intimate feel if the actors’ faces weren’t so horrifically made-up. That said, the visuals are unique and imaginative, creating a fantastical underworld of bizarre locales populated by even more bizarre characters. One sequence guest-directed by longtime Rodriguez-collaborator Quintin Tarantino — set in a car with Clive Owen and a very dead Benicio Del Toro — is a tour de force of computer animation (Del Toro’s half-severed head holds a conversation with Owen.)

Rodriguez, on the other hand, is at his best when paying attention to lurid details. It’s the little things that make “Sin City” so original: a split-second shot of a dirty drug addict lying in a pile of trash off to the side of a frame, or two fresh turds swimming in a gritty toilet bowl about to be used for a murder.

With such an emphasis on visualization, it feels as if the film’s actors were just allowed to cut loose — which leads to some bad performances. The worst comes from the usually brilliant Michael Madsen (Budd in “Kill Bill 2”) who recites his lines as if he were reading them for the first time. But the best of the ensemble cast manage to be wry while capturing the sensationalism and affected quality of a 1930’s radio show. Owen again proves himself, gritting his teeth with noir-ish flair; the young Alexis Bledel plays Becky, a young prostitute, with a gravity beyond her years.

When Rodriguez gets too heavy on the special effects, the film loses its dark edge. Some of the carnage sequences, especially one at a monastery, play out with the sterile energy of a videogame. Rodriguez fails to pace the action, unleashing too much too fast. By the time Hartigan sprays the colorful excretions of his arch foe all over a barn, numbness has irreparably set in.

In these final moments it becomes clear that “Sin City” is, at its core, blatantly meaningless. There are none of the deep breaths that Tarantino takes during “Kill Bill,” no moments of resonance or even true pain. Like the 1st century mock naval battles staged by the corrupt Roman government, the empty excess of “Sin City” bodes ominously for the future of American popular culture.

Even more terrifying is the fact that the first two-thirds are so damn fun. Throughout, Rodriguez’s spectacle feels like a sin to watch. At the end of the day, only one of the film’s own can sum up this exhilarating, demeaning, riveting schlockfest. In the words of Detective Hartigan, delivered to a terrified 11-year-old (his future sweetheart) as he aims his gun at a man’s crotch: “Cover your eyes, Nancy.”