"Would you like to drive our 13.6-liter/1000-horsepower V-16 sedan?" asked GM's Jeff Holland. Even though we knew there'd be extra-sticky driving rules and caveats regarding the $2 million concept's mechanical polish, there was only one possible answer: "Duh." Next thing we knew, we were piloting Caddy's sexy showstopper around GM's Milford, Michigan, Proving Ground. The Sixteen has been literally the biggest thing to roll onto the auto-show circuit this season. Bob Lutz, GM's vice chairman of product development and chairman of GM North America, says it's "a modern interpretation of everything that made Cadillac the standard of the world." But is it merely a lavish reminder of a once-glorious past or a relevant vision of the future? Enough scene-setting. What's it like to drive almost 19 feet and 16 cylinders of handbuilt concept car? Remarkably sweet. Entering the Sixteen requires punching a button on the key fob or lightly squeezing a microswitch inside the top of the front door. There are no door handles to clutter the Sixteen's lyrically curving body sides. Once inside, you're surrounded by the rich scent of fine leather, glints from polished walnut and aluminum, and thick carpets--woven of silk, no less. The driver's leather bucket is large, soft, and gently contoured. It power-adjusts to a comfortable position, surprising given the lack of ergonomic work that usually goes into a turntable toy. Likewise, the leather and polished-wood steering wheel can be powered into a just-right spot, which lets you easily read the speedo/tachometer gauge in the center of the dash. To start, step on the brake pedal and push a green button to the right of the wheel. You'll hear a strange, aircraft-style starter whine, then the mammoth V-16 erupts in a raggedy roar that quickly settles down to a somewhat bumpy idle (virtually no tuning was done on the powertrain's five engine mounts). As the engine starts, the instruments--including the clock--cycle and sweep their needles to calibrate themselves, emitting odd ticking and ratcheting clicks From inside the cabin, the engine's sound is neither the jungle murmur of a Mercedes-Benz SL55 AMG nor the near-silent thrum of a Bentley or Rolls. It's slightly rowdy and clearly coming from something in large displacement, particularly as you blip the throttle. Asked if they'd done any exhaust tuning, one powertrain engineer shrugs and says, "Well, we had four mufflers, and we threw two away." Ease into the throttle, and the car moves with a quickness that belies its mass and size. The automatic transmission has four gears, but we feel only two shift surges during our drive. This huge sedan glides precisely, with a catlike balance that puts us at ease. The steering feels light, and the car drives smaller than it looks. Give it more gas, and the result is a Mississippi River's worth of torque that surges the car forward. We back off to listen for crunching, grinding, or banging. Nothing--impressive for a machine whose primary purpose is to dazzle a show crowd. The Sixteen's ride is a bit jiggly, which doesn't say anything positive about the suspension, since the pavement is billiard-table smooth. While the XV16 concept engine architecturally resembles two GM OHV V-8s, its aluminum castings are unique. Displacement on Demand, titanium valves, and variable cam phasing = 1000 horses and 1000 lb-ft of torque. There isn't much turnaround room for us at the end of one particular Proving Ground road, but four-wheel steering comes to the rescue. Turning in opposite phase to the front wheels at low speeds, the rear wheels tighten the car's long turning circle to approximately that of a midsize sedan. The Sixteen isn't as polished as a production car; understandable, as that's not its mission. But it's easily the most refined concept car we've driven, which further teases us about what sort of production potential it, or some of its componentry, might have. The car's design represents an updated, and somewhat more elegant, variation on Cadillac's crisp-edged design language; perhaps some of the Sixteen's themes will show up on the upcoming Seville/STS and the next-generation DeVille. No, Keebler's not 3 feet 7; the Sixteen's wheels are 24 inches tall. Caddy concept blends heritage and futuristic touches with fine materials and beautiful execution Does anyone need 16 cylinders or 1000 horsepower? No. But the idea--like the engine itself--sounds simply wondrous.