VENICE (REUTERS).- If you thought that the world's biggest architecture show would be about buildings, this year's Venice Architecture Biennale has a few surprises in store.

Highlights include a steel ramp sneaking into a cloud, a pitch-black room where water falls from a swirling hose and a tower of metal cages from which one can jump into the void -- setting the tone for a show that, in a break with the past, this time focuses on people and space.

Set in the 16th century rope-making factory of the Venice navy, the Biennale mixes design with art installation and has pavilions from 53 countries, plus around 50 works from some of the world's top names in the business.

This edition is directed for the first time by a woman, Japanese architect Kazuyo Sejima. The winner of this year's prestigious Pritzker Prize, Sejima and her Sanaa studio are best known for designing the New Museum in New York and the undulating Rolex Learning Center of Lausanne.

The initial reaction by critics to her Biennale has been generally positive, with many praising the show as entertaining and atmospheric and welcoming the break with previous text-heavy, worthy exhibitions.

One of the most popular works is "Cloudscapes," by Japanese architect Tetsuo Kondo and engineers Transsolar, where visitors climb through layers of vapor on a 70-meter long ramp, and feel changes in temperature and humidity as they go.

"This is a place to experience a real cloud from below, within and above," say the authors.

"Sorry, It´s Broken"
Denmark's Olafur Eliasson has streams of water cascading in a dark room to be captured by strobe lights, Chile's Smiljan Radic and Marcela Correa have dug a shelter in a huge rock, while the Polish pavilion hosts a tower of metal cages from where people can leap, landing on a foam mattress.

Another installation that has generated a lot of buzz is a structure of barely visible thread-like wires by Junya Ishigami, who won the Biennale's Golden Lion award for best project.

Unfortunately, it has already collapsed twice -- once after a cat started having fun with it -- and some visitors complained that they found a message saying "Sorry, It's broken."

Those wanting more concrete examples of how futuristic design and architecture can make the world a better place should look at the "Seaswarm" technology that inventors say could clean up the oil spill in the Gulf of Mexico in less than a month.

Developed by M.I.T's Senseable City Lab, the Seaswarm is a fleet of small robots fitted with a conveyor belt made of a thin "nanowire mesh" that soaks up oil.

The special fabric can absorb up to 20 times its own weight in oil while repelling water and the robots have sensors to detect the presence of pollutants.

Once absorbed by the conveyor belt, the oil can be removed and the fabric re-used, making it more efficient and less expensive than current skimming methods, its creators say.

The Architecture Biennale runs until November 21.

(Editing by Paul Casciato)