WHAT IF MICHAELANGELO HAD PICKED UP skateboarding and moved to Big Sky Country? The result might have looked something like Bottega Montana, a line of exquisitely solid tables, desks, stools, and—yes—longboards designed and manufactured by Italian transplants Marco and Francesco Gillia in tiny Lima, Montana.

"When we start designing a new piece," says Francesco, 33, "we picture the Colosseum, and how it has lasted 2,000 years." He's not kidding: Thanks to the Gillias' revolutionary joinery work, which locks together thick slabs of sustainably harvested white oak and black walnut without a single screw or nail, a Bottega Montana piece hardly needs an extended warranty. While the sheer massiveness of the designs—the monastery-style dining-room table weighs 350 pounds—gives them an almost medieval flavor, the exposed tongue-and-groove joinery lends a clean midcentury-modern look.

The Gillias first fired up the shop tools two years ago, after Francesco, who'd been working as a footwear designer in Hermosa Beach, California, invited his brother Marco, 30—then working toward his architecture certification in Italy—to join him on a new venture. The pair set up on the family ranch, in southwestern Montana, pulled together some instructional DVDs and how-to books, and began experimenting with tables and desks. Despite their hurried and informal schooling, they were soon turning out creations unique and refined enough to catch the eye of modern-furniture giant Herman Miller, which will exhibit several of the pair's Charles Eames–inspired stools at its National Design Center, in Chicago, starting in June.

As for the longboards, "they are gorgeous; there is nothing like them in the industry," confirms Dan Gesmer, who supplies hardware for the boards and sells them online at www.geoskate.com for between $543 and $675. "The tongue-and-groove joining technique is straight out of the Renaissance." Just like the guys who build 'em.