Prefab structures jut out from the roofs of Paris’ charming architecture, adding affordable real estate to the densely-packed, land-scarce city in the only way possible: building up. While other cities across the world are knocking down one older structure after another to build shiny new condos that stretch up into the sky, the new units are often too expensive for the average urban resident, and significantly alter the historic character of each individual place.

Whether historically significant or not, the older buildings in most cities help give each location its own particular flavor. Razing them to throw up generic condominiums for people with upper-middle-class incomes not only displaces existing residents, it erases much of each city’s personality. A new project called 3BOX aims to compromise.

Stéphane Malka Architecture has designed a series of rooftop prefabs that work within the context of Paris’ new property law, the Loi ALUR, which aims to construct 70,000 new dwellings per year while also stabilizing rent. The law comes with a relaxation in planning and zoning, enabling new rooftop construction.

While many of the new dwellings built under Loi ALUR will go on brownfield sites, like those currently owned by French rail company SNCF, others will have to be woven into the fabric of the city in more creative ways. ‘Les Toits Du Monde,’ or the Roofs of the World, offers three different prefab structures bolted onto existing buildings with steel supports.

Not everyone will be crazy about altering 19th century buildings with these prefab boxes, no matter how science-fiction it may start to look, but the rooftop terraces help make them more attractive, and they could be a good option for structures with less aesthetic value.

Far from its typical location in the woods and other remote places, an archetypal cabin looms over the bustling city of Athens from its rooftop perch two meters above the top of most high-rises. Proposed by Panos Dragonas and Varvara Christopoulo, the elevated urban hut brings a structure with a rural connotation representing quiet and solitude into an environment that’s nearly the exact opposite.

Instead of hills and trees, the hut looks out onto a landscape of man-made design. But the designers posit that these urban spaces, busy as they may be, can still provide a space for meditation and peace – as long as you go to extremes.

Urbanization has made isolated spaces hard to come by, so the dream of escaping to a cabin in the woods is not as achievable or even idyllic as it once was. This project emphasizes how much the world has changed as our cities have grown, replacing nature with streets, skyscrapers and antennas.

The hut is a mere nine square meters (96 square feet) and lacks any modern amenities, offering only a few platforms for sleeping and sitting, much like a camping shelter in the wilderness.

“The urban hut creates a voluntary isolation cell over the ruins of the new Great Depression. The hut returns to the city both as a primary form and as a standard of minimum living, and establishes a heterotopia in the stepped skyline of Athens.,” say the architects.

The man who built his very own luxury mountain palace atop a condo tower in China – illegally – is hardly alone in his endeavors. A Chinese microblogger spotted what looks like another unsanctioned resort on the roof of a 21-story luxury apartment complex in Shenzhen, complete with lush landscaping and a temple.

While it’s clear that the stone penthouse was built without permission, this particular rooftop paradise is shrouded in mystery. It has been situated on top of the apartment building for at least three years, but nobody knows who it belongs to, or why it appears to be under such tight security, including cameras, guard dogs and a fingerprint scanner.

A video taken from a helicopter gives us a glimpse at the complex, which appears to include gardens and a pond as well as the gold-tiled temple itself. Tenants fear the suspected illegal construction could jeopardize the structural integrity of the entire building. Neighbors report that golden sheets of joss paper, which is burned to honor ancestors, occasionally floats down from the temple’s perch, leading them to believe it’s used for traditional Chinese religious practices.

According to the South China Morning Post, a local property owner told reporters that the person responsible for the temple might be the director of Nanshan district’s Residential Property Management Office, a man named Xiong. “We once had a meeting [regarding the temple] and required it to be demolished. We put up notifications. But [Xiong] installed a security door and refused to let demolition people near [the structure.] The [problem] has still yet to be resolved.”

Sailing through the clouds in a riverboat perched atop Queen Elizabeth Hall in London may sound like a strange and surreal dream, but some travelers are set to do just that as ‘A Room for London‘ opens to guests. The temporary boat-shaped apartment was commissioned by Living Architecture to celebrate the Olympic year of 2012.

The winner of a competition that saw entries from five hundred architects and artists from around the world, this design by David Kohn and Fiona Banner was inspired by the riverboat Roi des Belges, captained by Joseph Conrad in the Congo in 1890, which served as the basis of his novel Heart of Darkness.

A Room for London is “of no distinct era in terms of its style, neither recognizably modern nor old-fashioned,” Living Architecture notes. From its perch atop Queen Elizabeth Hall at the Southbank Centre, it proffers views of the Thames and will be a prime location from which to gaze out at the bustle of the city when the Summer Olympics start in June.

The riverboat room features an upper viewing deck and a striking magenta-and-turquoise interior including a double bedroom, kitchenette and library. The first run of bookings, which run through June, has already sold out, and the second run, for July through December, go on sale today, January 19th 2012.