The Cadillac Celestiq starts at $340,000. It's a handbuilt ultra-luxury sedan with its sights set on Rolls-Royce and Bentley, and the first of its kind in the General Motors lineup. While nobody in the press has had the opportunity to drive one yet, I recently got the chance to ride shotgun in the Celestiq to see what all the fuss was about. 

The Celestiq is the brand's most audacious car in recent memory. Not only does it stand alone in the automaker's lineup price-wise, but it's only the second high-end electric luxury car after the Rolls-Royce Spectre. The Cadillac is also completely bespoke and the only EV in GM's current lineup to get a unique battery module design, which enables a thinner floor.

That long, thin battery is possible because the Celestiq is a huge car. Its scale and proportions aren't immediately obvious in photos, but standing alongside it, I'm in awe of its size. I'm a few inches shy of six feet, and the 23-inch wheels are nearly up to my waist. At the same time, the roof of the car sits extremely low—well below my shoulders. 

Pressing a button on the car's B-pillar swings open the passenger door, and it latches shut with a soft close. I wasn't driven long enough to get a great judgment on how comfortable the seats were, but they certainly weren't uncomfortable. But the most striking thing about sitting reclined in the Celestiq was how roomy and quiet it was.

The interior is unlike any other car I've experienced in terms of its size and shape. It's extremely wide and long inside, yet the low roof and sleek window openings make it quite cozy. The flat floor also gives a concept car vibe to the whole experience. My Celestiq had about as basic an interior as any prospective owner might spec—black-on-black with some doubtlessly real walnut trim—but it still felt special. You could even see all the way back into the carefully upholstered trunk, adding to that sensation of spaciousness.

The burnt orange exterior was one of the better colors I've seen on this car, which was still a development mule. Behind the wheel was a GM software integration engineer. I asked him what didn't work on this particular vehicle, and he said it was pretty much ready to go. On my side of the center tunnel was some electronic diagnostics equipment, but besides that, the vehicle seemed complete. 

Browsing through menus as fast as I could, there weren't any features I tried that didn't function, including the variable-tint roof. With a single press, all the panels either go dark, remain clear, or can be adjusted individually to one of four levels. There was also an automatic setting.