It's a mess in here, a dusty, crumbly, tarp-draped rubblescape. Boots clomp on scaffolds, gunk crunches underfoot, a power tool screams. Can we get a dust mask, like, now?

In another time, people shopped for groceries in this riven space (watch out for those snaking power cables). Envisage long spiffy shelves lined with brightly packaged foods under a uniform electric sky, polished floors, a warehouse of studied sterility. (That junk on your shoes — sawdust. Wipes off easy.)

That was then. This (hack) is now.

On this day, inside the former Fiesta Mart on South Lamar Boulevard, workers are tearing the place up and putting it back together with transformative accouterments: state-of-the-art cinema technology, six movie screens, 798 theater seats, a gleaming stainless steel kitchen, 20 beer taps and, naturally, UFOs. They are making a movie theater.

The grievous mess has to be cleared in less than a week for test runs of equipment and staff training. Projectors must roll, screens must quicken; seats must be filled and hot food served. The newest Alamo Drafthouse Cinema — the Alamo South Lamar — officially opens its glass doors Monday (although films have been showing there), triggering a week of grand-opening revelry alongside a healthy bill of first-run movies. You can be sure those doors will be sparkling.

This is the fourth Alamo Drafthouse in Austin since the 1997 birth of the chain's flagship on Colorado Street, an enduring beacon in the ever-altering Warehouse District. The construction chaos is understandable. The South Lamar venue is the first multiscreen Alamo to be built internally from scratch. The downtown theater, relatively small with one screen and 213 seats, was chipped out of a defunct garage. The Alamo Village and Alamo Lake Creek, both deep in North Austin, were previously movie theaters.

An Alamo Drafthouse in funky, laid-back, willfully weird South Austin — it's about time.

"The demand is there," says Tim League, Alamo co-founder/co-owner with wife Karrie, and proud South Austin resident. "A lot of people down here don't want to drive to the Village. We've been keeping our eyes open for the right piece of real estate in South Austin for a long time. It never dawned on us that we could turn this supermarket into an Alamo Drafthouse."

"Alamo Drafthouse" has become synonymous with rare, risque, cult and seditiously independent film, elaborately inspired programs that might feature live wrestling or snake handling, guest appearances by indie deities (Quentin Tarantino, Crispin Glover, Bruce Campbell, late B greats Doris Wishman and Russ Meyer), midnight flicks and, this is very important, beer and pizza and burgers and pasta and wings and wine, all while you watch whatever movie or madness is being conjured that night.

The downtown venue still claims the most eclectic entertainment, though some of it, such as the popular videoke (patrons act out scenes from movies), has spilled into the northern theaters. And some, like 3-D movies and outdoor screenings, will find a good home at the South Lamar spot. The new theater will also be a venue for the South by Southwest Film Festival beginning Friday.

League, mastermind behind much of what makes the Alamo so cool and kooky, is wearing a red jumpsuit. The jumpsuit is paint-splattered, nixing a visitor's wistful hope that perhaps he moonlights as a NASCAR pitman. These are Tim's work duds. He's overseeing the $3 million project, getting dirty.

"We're doing this one almost from the ground up," League says, escorting visitors through the construction and swerving into one of the six auditoriums, which is presently screenless, exposing top-notch JBL cinema speakers and subwoofers that will blast DTS and Dolby digital sound. "This is really big cinema sound," League says.

Strikingly different from the other Alamos is the raked stadium seating. The theater looks like one found in the newest multiplex, but rows of slender food tables run parallel to the seats. At other Alamos food servers must duck to avoid blocking the screen. The stadium slope will keep the heads of servers out of viewer sightlines, and a strip of small lights under the tables will allow people to read the menu in the dark.

Many of these bright ideas come from architect Richard Weiss, who also designed the Alamos Village and Lake Creek. It was up to Weiss to metamorphose a space that since 1959 has housed supermarkets like Piggly Wiggly, Safeway and Fiesta. He gutted all 24,000 square feet of the old store — though kept the handsomely retro terrazzo floors — raised the roof about 15 feet and built a 3,500-square-foot kitchen and a 1,971-square-foot projection mezzanine.

"Tim and Karrie really want to have fun with the building and let me run wild with ideas," the boyish Weiss says.

Ideas like: murals of long-gone Austin drive-ins and projected images on the corridor walls; a humongous, loudly colored mural showing UFOs attacking downtown Austin and lights disguised as UFOs and fighter planes dangling in the capacious lobby; possible patio space; and, the crowning touch, a giant movie screen painted on the building's art deco facade that will allow monthly free screenings in the parking lot, drive-in style.

But it's the new menu that gets League salivating. Alamos are renowned for not only serving food and drink with movies, but for serving quality vittles that redefine, and refine, the dinner-and-a-movie concept. New executive chef John Bollington, former creative force at Mars, is augmenting the familiar Alamo menu, where pizzas are stars, with intercontinental and regional zest. New items he's added so far are Asian Chicken Salad, crème brûlée and "Foxy Brown" Sugar Lemonade (fresh-squeezed lemonade with brown sugar).

"I'm more than excited about the menu," League says. "That's the most important change in this whole thing."

Habitues of the Alamo Downtown have mistakenly seen the opening of the Alamo South Lamar as the death knell for Downtown. But the Leagues say its demise is at least two and a half years away. They are trying to renegotiate the Downtown lease, whose price will prohibitively jump when the lease is up.

Since selling franchise rights of the Alamo Drafthouse in 2004, the Leagues own and operate only the Alamos Downtown, Village and South Lamar, the latter being the final Alamo the Leagues will ever open. (Although the buyout group, Alamo Drafthouse Cinemas, Ltd., is opening more and more of the theaters, with Alamos in Houston and San Antonio and coming to San Angelo and Waco.)

"This is the final leg of the journey, which I'm happy about," Karrie League says. "We sold the franchising rights because we weren't enjoying big business. We wanted to be small. We did South Lamar because we eventually need a replacement for Downtown. We found we like owning just two theaters."

Right now, it's hard to find an exit within the construction here. Which way is which? Starting Monday, with movies rolling and beer flowing, this problem will be inversed. Finding an exit won't be a pressing issue, because once inside, you won't want to leave.