This glass box lookout will put your fear of heights to the test

Visitors lie with their feet in the air, sit on the glass floor and walk to the edge of a transparent box as they pose for photos in a new sky deck on the 42nd level of Sao Paulo's tallest building, the Mirante do Vale.

Called the Sampa Sky, the dizzying lookout officially opens on Sunday, but some people got a sneak peek on Wednesday.

"I think it's beautiful, I love it. It was something that was missing in Sao Paulo," said Sylvia Barreto, who admitted she was a little scared when she stepped out into the glass box.

The deck, nine floors below the top of the 170-metre-high building, was inspired by Chicago's Skydeck, on the 103rd floor of the Willis Tower.

"It's an incredible sensation," said Deisi Remus. "I am scared to death of heights, I must confess, but I worked through the fear. After the first step it was incredible, it is incredible to see the city from this height."