The Eden Project is pushing through plans to create a desert climate section with a third biome to help deal with huge visitor numbers.
The £86 million Nicholas Grimshaw and Partners project near St Austell in Cornwall had been expected to attract 750,000 people in its first year.
But the project drew 1.5 million visitors in the first six months. This has led to congestion, so the Eden management team has speeded up plans for additional facilities; now being considered is a third biome costing £20 million, representing the semidesert climate of Arizona.
Paul Travers, media director for Eden, said: 'On a sunny day we can easily cope with 10,000 people on site, but when it is raining, everyone wants to be inside the biomes and there isn't enough room. We are speeding up the plans to provide better facilities for our visitors, but it is still very early days.'The Eden team is also considering plans for an on-site hotel, a conference suite and student accommodation.
News of the plans came to light during a meeting to discuss the future of traffic management around the project. The meeting, at Cornwall County Council, is considering ideas such as a new park-and-ride scheme to alleviate congestion.