Ten countries - including the Bahamas - are participating for the first time with their own dedicated pavilions in a fair that runs until November 24. "The national pavilions are fantastic because they give us a glimpse of the diversity of the world … a world of exceptions," says Gioni.

The Vatican is also debuting. The Holy See's pavilion is in the Arsenal, or old shipyard site. While the three rooms are based on the relatively orthodox themes of "creation", "uncreation" and "recreation", the use of video and a pervasive thumping heartbeat soundtrack add a modern element.

The Bahamas pavilion holds a surprise for anyone expecting warmth and sunshine. Nassau-born artist Tavares Strachan's show includes a 14-hour video of his recent trip to the North Pole and two freezer pods containing blocks of ice: he brought one back from the pole while the other was made to a specific formula to resemble polar ice as closely as possible.

"I grew up on an island that was 24 miles by seven miles [38.4km by 11km]. It was tiny. So if you got on a bike and you started riding, you hit the edge and you were like ... 'what else am I going to do?' Exploration was kind of a natural part of theway I thought about the world," Strachan says.

Gioni themed the 55th iteration of the Venice show on the "Encyclopaedic Palace", a design filed for patent by eccentric Italian-American Marino Auriti in 1955 for an imaginary museum, 137 storeys high, that would house all worldly knowledge in one place. Auriti's ambition was never realised, but the biennale has set a more realistic goal, giving an introduction to art that's rarely seen abroad.

"I hope that we are going to be an introduction to Iraqi art," says Furat al Jamil, one of 11 artists in the Iraqi pavilion, which is set in a traditional Venetian apartment overlooking the Grand Canal.

"These are samples. Modest samples but genuine and sincere," says Jamil as she shows , a sculpture made of suspended honeycomb frames dripping into a broken antique pot.

Jamil's colleagues Yaseen Wami and Hashim Taeeh have furnished the apartment's bedroom in cardboard, right down to the bedclothes. Cartoonist Abdul Raheem Yassir's politically charged illustrations hang on the walls, near Jamal Penjweny's series of photographs titled .

Chinese dissident artist Ai Weiwei is represented twice in Venice this year, despite being unable to attend in person. His mother came in his place to unveil his new piece, a series of sculptures called depicting his detention in 2011.

The setting brings another dimension to Ai's new piece, says art gallery director Greg Hilty, who collaborated on the project installed at Sant'Antonin church. "If you saw this in a museum you would appreciate the minimalism, you would appreciate the politics," Hilty says. "But the church connects it to the stages of the cross, to the lives of the saints, it gives it a more universal story or meaning."

The biennale continues to attract artists and viewers partly because of its own history, says Jeremy Deller, the Turner prize-winning artist chosen to represent Britain. "This is as good as it gets really, for an artist," says Deller, whose show starts with two huge scrolls - inscribed with lyrics of by David Bowie - hanging on both sides of the main door.