There are rooftop tents you can mount on just about anything. There are campers of modest size that you can drive or tow. There are clever home-built campers made out of everything from old school buses to a Nissan Versa. There are large motorhomes with small garages and space to stretch out. And then there are insane luxury motorcoaches like this 2007 Prevost Featherlite and yes, it actually has a basement.
Of course, it's not a subterranean basement, but it is living space beneath the floor that is accessible from outside and inside this rig. Not that you'd ever want to leave the luxurious interior filled with wood, chrome, mirrors, and high-end materials, but sometimes everyone needs a little escape room. That's pretty much what this is, as demonstrated by the giddy narrator in this video from RVing with Andrew Steele on YouTube. Presumably, this is Andrew on camera and as you can see from the screenshots below, a small hatch in the floor leads to a rather cozy bunk that spans the width of the RV.
The bunk basically occupies a storage bay, but it's not a sleeping bag stuffed into a closet. The space is trimmed with nice materials and fitted with lights and two television screens, and while the hatch in the floor seems a bit sketchy, the large exterior door opens for easier entry. For that matter, several of the exterior bays are designed for outdoor entertainment, with one including a second refrigerator and freezer and another featuring a big television. Of course, that's in addition to all the entertainment gear inside, not to mention two toilets, three sinks, and a separate master bathroom with a shower.
As you'd expect, such luxury in a motorhome doesn't come cheap. These rigs easily pass the £1.5 million mark when new, though this 14-year-old model with 97,000 miles is currently for sale at just £365,000.