The idea of super-dense cities building new structures on top of old buildings has been kicking around sci-fi novels and architecture circles for decades, but the idea still isn't ubiquitous. In Austria, the owner of a 1950s-era building is giving it a shot.

Hotel Daniel Graz is a boutique hotel in Graz, housed inside a hotel designed in 1955 by architect Georg Lippert. Lippert's classic postwar building had fallen into decay after serving its time as a luxury five-star destination next to the Graz train station, and the new owners—who run a boutique hotel by the same name in Vienna—have restored the historic building to its former glory and made some radical changes, too. Like, say, adding an entirely new guest suite: A 473-square-foot prefab cube that sits on the existing roof.

The pod was fabricated by a company called LoftCube, which markets its prefab pod structures as moveable homes and offices with small environmental footprints. Inside the structure, visitors will find exactly what they'd expect to find inside a hotel: A bed, a bathroom, a TV, a sitting area. One major difference: When they leave their room, they'll be stepping down onto the roof of the hotel itself.

This is the first permanent rooftop installation from LoftCube, which is now a few years old, as well as the company's first hotel-borne pod. It'll surprise no one that while the concept of putting new housing on top of old housing is symmetrically pleasing, the reality is nearly as complex as building an entirely new structure—if not more so. The pods themselves run from $150,000 to $250,000, not including the cost of an airborne installation.

The pod arrived via rail in mid-September, after a long permitting and design process. By November 1st, it was fully completed—certainly a shorter time frame than a new building, but one that included transporting the room and using a mega-crane to lift the new room onto the aging building's roof.

Sure, it's an expensive way to expand a building—not to mention a historic one—but the photos make it look like an amazing space. And if it makes prefab a little more glamorous, then what's the harm? [Hotel Daniel Graz; Yatzer]

All images courtesy of Hotel Daniel.