Cornwall's multi-million pound tourist attraction, the Eden Project, has announced plans to build a third giant dome.

The attraction, which currently has two giant plastic domes, recreates climates from around the world for a huge variety of plants.

The third dome will look at arid regions and will be called Dry Tropics.

Models and diagrams of the plans went on show on Tuesday.

We like to make learning fun and in a world that can be grey and frightening, people have found that a resonant tone

Gaynor Coley, managing director

Other new buildings at the �86m project will be a Learning Lift and a visitor gateway.

Local people are expected to protest about the increased traffic and pollution resulting from the expansion of the site.

The cost of the project is estimated at about �100m.

More than 1.3 million visitors have been to the project over the summer, and research estimates the project has contributed �160m to Cornwall's economy.

Gaynor Coley, the managing director of the project, said it had always planned to build three biomes.

"If you come here on a busy day and you see the capacity of 750,000 bursting at the seams, you would agree we need to get more covered space onto the site.

To be honest, we don't want any more visitors. We have a comfortable amount

Tim Smit

"This will build us double that capacity to two million visitors making sure everyone has a good day out," she said.

She said the new biome would look at desert plants and how people survive without water.

"We like to make learning fun and in a world that can be grey and frightening, people have found that a resonant tone."

Eden Project chief executive Tim Smit said the point of the new biome is not to attract more visitors, when asked about concerns over possible increases in numbers.

He said: "To be honest, we don't want any more visitors. We have a comfortable amount.

"It's a bit too compressed at the moment. We need more space to enable them to relax more and learn more about what we're really about."

The plans have gone on display

The biomes - the largest of which could house the Tower of London - house conservatories with plants from round the world.

Boardwalks lead visitors through 12,000 plants, taking them from the Oceanic Islands to Malaysia and from West Africa to South America.

The Eden Project is located in a former clay pit near St Austell.

It has become Britain's third most popular tourist attraction since it opened in March last year.