One of the biggest homes in U.S. history is rising on a Los Angeles hilltop, and the developer hopes to sell it for a record US$ 500 million. Nile Niami, a film producer and speculative residential developer, is pouring concrete in L.A.'s Bel Air neighborhood for a compound with a 6,9 thousand square meter main residence and three smaller homes, according to city records. The project, which will take at least 20 more months to complete, will exceed 9,3 thousand square meters, including a 465 square meters master bedroom, a 30-car garage and a "Monaco-style casino," Niami said. Niami's project, on a 1.6-hectare hilltop lot, will have 360-degree views of the Pacific Ocean, Beverly Hills, downtown Los Angeles and the San Fernando Valley. Plans called for removal of almost 30,600 cubic meters of earth, the equivalent of an American football field covered by 6 meters of dirt. Niami's mansion is set to be the largest built in the U.S. this century, surpassing Versailles, a 8,3 thousand square meters chateau in Windermere, Florida, under construction for David Siegel, founder and chief executive officer of Westgate Resorts. Estates with views of the Los Angeles basin are the California counterpart to Manhattan's penthouses or London's Mayfair manors, drawing a global cast of financiers, technology tycoons and celebrities who collect trophy homes like works of art. Around the world, five properties sold for US$ 100 million or more last year, and at least 20 others have nine-figure asking prices, Christie's International Real Estate reported last month. The priciest home ever sold was a US$ 221 million London penthouse purchased in 2011, according to Christie's. The most expensive properties on the market include a US$ 750 million rancho in USA, a US$ 425 million estate in France's Cote d'Azur Villa Leopolda, an almost US$ 400 million penthouse in Monaco and a US$ 365 million London manor.

The world's largest hotel is being planned for Mecca, Saudi Arabia, a remarkable structure that will rise out of the desert and apparently contain 10,000 rooms for worshippers. The hotel will be part of a mixed-use development at Abraj Kudai, a US$ 3.5 billion project intended to look like a desert fortress that encompasses a ring of towers standing on top of a podium. It is due to be completed in 2017 and is being situated in the Manafia area of Mecca's central zone, just 2.2 kilometers south of the Masjid al-Haram (holy mosque). DesignMENA reported that the hotel will have 10,000 rooms in 12 separate towers, which are 44 stores high that will also include 70 restaurants, rooftop helipads, royal floors and a full size convention center. Two of the towers will offer five-star facilities, according to the hotel's architects Dar Al-Handasah. The other ten will provide four-star accommodation. The interiors are expected to be in keeping with the opulent style found elsewhere in the region. The site, which will also include residential facilities, a shopping mall and plenty of car parking for those visiting the mosque and black Kaaba, has an approximate total site area of 60,000 square meters and a total built-up area of 1.4 million square meters. The world's largest hotels up until now have been in Las Vegas. The Venetian and The Palazzo, which operate as a single hotel, offer 7117 rooms. The MGM Grand in Las Vegas is close behind in terms of number of room keys, with 6,852 rooms available.

It's traditionally played on grass and clay, but could tennis matches one day take place in a waterproof bubble in an "underwater Wimbledon"? An architect Krysztof Kotala from Polish firm 8+8 Concept Studios has released designs for an ambitious project to build an underwater tennis court off the coast of Dubai. He showcased some computer-generated images of the proposed tennis court. An underwater tennis complex could be built just offshore in the Persian Gulf, between the Burj al Arab and the Palm Jumeirah islands. Part sports arena and part aquarium, the eccentric concept for the seven-court complex calls for a rooftop coral reef, which would bring an abundance of sea life to the area for spectators (and players) to view. During his interview to Arabian Business Kotala told that the idea had strong commercial potential and would combine the best of "technology, ecology and sport." An architect is currently seeking investment from local backers to make the concept a reality. "There is not an investor but I would like to get interest as I think it is a good idea," he told Arabian Business. However, although the underwater sports concept looks stunning, engineers have poured water (excuse the pun) on the idea that such a tennis court could be built with current technology. Sarah Fray, director of engineering and technical services at the Institution of Structural Engineers in London, explained that one of the biggest challenges would be to create the large span of glass to cover the court. This would have to be at least 33 meters wide to accommodate the court and spectators. Currently, flat panels of glass can be manufactured in single pieces around 10 meters long - such as panels used in Apple's store in Turkey - but new machinery would have to be invented to make larger panes of curved glass, the type of which would be needed for the design. Another challenge is how to get to the tennis court. She explains that there would have to be a way for the structure to be connected to the surface. However, she conceded that the arched shape of the underwater court is a good idea because it's the best way of resisting pressure, the likes of which would be vast, particularly if the court was submerged at a decent depth beneath the waves. Will Stewart, a Fellow of the Institution of Engineering and Technology (IET) added that the design may not appear as bright inside as the concept images suggest. He explained the glass would have to be many meters thicker at the edges than at the center of the arch, so views of the ocean would not be as bright as they are in the concept pictures. Dubai is no stranger to unusual tennis courts. In 2005, a court was built atop the 305 meters tall Burj al Arab hotel to promote the Dubai Tennis Championships. Besides this Dubai is known for outlandish construction projects including man-made islands and the world's tallest building. It also already has a restaurant - Al Mahara - that's underwater. However the technological challenges are big, but the human challenges are bigger. And in future everything is possible.

Last year architect Adam Kushner announced plans to build the newest 3D-printed estate in Gardiner, New York. Recently, the architect and CEO of D-Shape, James Wolff, presented new renderings of Kushner's project at 3D Print Week NY that show an even more over-the-top plan than we even imagined. According to the project details, the entire structure will be built using a modified version of Enrico Dini's oversized D-Shape printer. And we're not just talking one basic house here. No, Kushner is determined to build a massive swimming pool, pool house and car port to go along with the four-bedroom, 223 square meters home, and eventually creating one enormous 3D-printed estate. Although still in the planning stages, the residence is slated to be built about 137 kilometers from New York City on a 20 thousand square meters parcel of land that Kushner and his wife purchased three years ago. Kushner explained that it was the plot's naturally rocky landscape that inspired the ambitious 3D design. "The materials on the site will be used to form the pieces of the site, which reflect the very characteristics of the site, which stems from the materials found on the site," explained Kushner. "I think it's a perfect circle." The 3D design scheme stems from the geomorphology of the rocks found in the area, inspiring Kushner to print the entire estate using the rocks for aggregates in the building process. According to 3D Print, using Enrico Dini's D-Shape printers, which differ from the common fused deposition-based models, will allow Kushner to print the necessary materials using on-site resources such as sand, which will be combined with a magnesium-based binding agent. Kushner is still waiting for the delivery of the large-scale 3D printer from Italy. However, if all goes well with US customs and NATO approval, the machine should be on-site in May and the team hopes to begin the first trials and test prints using the new machine by June. Once all of the kinks have been worked out, the team expects to begin 3D printing the pool, followed by the pool house and car port. The last piece of the 3D puzzle will be the most challenging - printing and building the 223 square meters house itself. As far as why this project is so important to Kushner, he explains that by starting on such an ambitiously-sized estate, the 3D home building process can later be used for far more important and diverse tasks, such as producing affordable housing or emergency shelters. "If we can build a pool, then we can begin building reefs, and repair bridges, bulkheads and other underwater structures which there is a huge worldwide need," said Kushner. "The thought is that if we can build a pool house and modest enclosed structure, then it is a short step to building emergency shelters and low cost housing units." Recently a Chinese company WinSun has successfully 3D printed a five-story apartment building and a 110 square meters villa from special print material. China's newest mansion is not only made from recycled materials, but the sprawling 110 square meters home was made with 3D printing. The luxury mansion was 3D printed in layers, using recycled stone and construction waste. Last year the Dutch company DUS Architects developed 3D-printed house using bioplastic.

For several years now, tech companies have been at work to develop clear solar panels that can double as windows, but the Current Window provides a gorgeous stained glass twist on that idea. Created by Dutch designer Marjan van Aubel, the window generates an electrical current by harvesting the energy created when sunlight hits a colored pigment-much like photosynthesis in a plant-and sends that power to a USB port in the window ledge. According to van Aubel, "The glass pieces are made of 'Dye Sensitised Solar Cells', which use the properties of colour to create an electrical current-just like photosynthesis in plants. Similarly to the various shades of green chlorophyll absorbing light, the coloured window panes harness energy." That energy can then be used to power small appliances; a USB port in the window ledge can charge a standard smart phone in about seven hours. But that's just with one relatively small window-the designer hopes that if replicated on a larger scale, say over the vast colorful facades of churches, or in schools, the Current Window could provide clean energy in a uniquely beautiful form on a much larger scale.