Nasa is holding a competition with US$ 2.25 million in prizes to find the best sustainable habitat that can house astronauts on deep space exploration missions. The US space agency is challenging designers, architects, engineers and 3D printing enthusiasts to not just build sustainable housing that can be quickly 3D printed and replicated, but also to make sure that the materials used are both recyclable and indigenous to Mars. The new project will feature two different stages. The first stage, which is currently open for registration, requires entrants to design an architectural concept for a habitat that makes use of 3D printing, with 30 submissions shortlisted and a cash prize of US$ 50,000 to be given out. The second stage of the competition opens for registration on 26 September and entrants can choose to enter either or both of the two challenges set, which each carry a prize of US$ 1.1 million. The Structural Member Competition (Level 1) requires entrants to develop the fabrication technologies needed to manufacture structural components either from a combination of indigenous materials and recyclables, or indigenous materials alone. Meanwhile, the On-Site Habitat Competition (Level 2) challenges competitors to build full-scale habitats using indigenous materials or indigenous materials combined with recyclables.

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.

The biggest ranch in America that stretches over 510,000 continuous acres - that's 796 square miles, (2060 square kilometers) making it a plot of land bigger than the island of Oahu - has gone on sale for US$ 725 million. Realtors are hoping the Waggoner ranch in north Texas will become the most expensive estate in the world - after slapping the huge price tag on it in the hopes of attracting a Silicon Valley entrepreneur or oil tycoon. Cattle baron Dan Waggoner established the estate in 1849 - and it has operated with its backwards 'D' logo ever since. The estate includes the 2060 square kilometers ranch spread over six North Texas counties, with two main compounds, hundreds of homes, about 20 cowboy camps, hundreds of quarter-horses, thousands of heads of cattle, and 30,000 acres of cultivated land, according to Dallas-based broker Bernie Uechtritz, who is handling the sale along with broker Sam Middleton of Lubbock. Oil was discovered on the property in 1902 and there are now more than a thousand wells spread across the property.

Pablo Picasso's granddaughter is selling his villa in Cannes and 126 of his ceramics as she tries to shake off unhappy childhood memories of the artist. Marina Picasso, 64, remembers being taken to the gates of the grand three-storey house, La Californie, by her impoverished father, Paulo, to beg for handouts from an indifferent Picasso. The sale "will be a way for me to turn the page on a rather painful story," told Marina Picasso. She has reportedly received an offer of nearly US$ 172 million for the 1920 villa that she inherited at the age of 22, along with an extensive collection of his works. Sotheby's expects the ceramics to fetch up to US$ 9.2 million. "It's not a house where I have a lot of good memories," she said. "I saw very little of my grandfather there. With hindsight, I understand that he may have been captivated by painting and nothing else was more important to him. Except when you're a child, you don't experience it like that." Picasso bought the villa in 1955 and painted one of his most famous works there, The Bay of Cannes. He moved out in 1961 after his view of the sea was blocked by a new building. Marina Picasso renovated the villa in 1987 and renamed it the "Pavillon de Flore", although it is better known as "La Californie". Marina Picasso says the sale will help her broaden her philanthropic projects. She funds a children's hospital in Vietnam and programs to help troubled teenagers and the elderly in Switzerland, where she spends much of her time. Picasso lived at La Californie with his second wife, Jacqueline Roque, who barred Marina Picasso and her brother Pablito from the artist's funeral. Pablito Picasso committed suicide a few days later. Marina Picasso's father was Picasso's son by his first wife, Olga Khokhlova, a Russian-Ukrainian ballerina. He was humiliated by being forced to work as the artist's chauffeur.

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.