It's hard to get a sense of scale from these images, but this car is huge. It's very likely built atop a heavy-duty truck platform, which is necessary due to the thick armor-like bodywork that's hermetically sealed to keep POTUS safe and sound. It's hard to tell for certain, but it appears this Beastie is riding on Goodyear Regional RHS II tires, which would otherwise be used on trucks and buses. Translation: this thing is heavy.
The Beast is ostensibly badged as a Cadillac, and it wears the latest version of Caddy's corporate grille, badge, and upright headlamps at the front. From the rear, there's a hint of Rolls-Royce Phantom, with rear glass that tapers elegantly into the deck lid. In between is a massive slab-sided passenger compartment that's rumored to seat as many as seven passengers.
These shots were snapped at GM's Milford Proving Grounds. It seems The Beast is undergoing some high-speed tests, though high-speed here is relative. Those Goodyears are only rated for 70 miles per hour or so, and we doubt the big 8.1-liter gasoline-fueled V8 engine is geared to push the President much faster than that, anyway.