The proposed redevelopment would see the current concrete building replaced by a cafe finished in stone and glass, costing around �7m.

The summit of Snowdon attracts 400,000 walkers and train visitors each year, but the existing building has been described as "the highest slum in Britain" by Prince Charles.

Previous attempts to redevelop the cafe failed because of a lack of cash - the details of how this proposal will be funded are still to be revealed.

The new cafe will incorporate non-reflective glass, with the roof line softened to blend in with the stone at either ends, and the colour of the stone will be close to the greyness of the sky.

The artist's impression of what the new cafe will look like

The current cafe, which was designed by William Clough Ellis - the man behind the Italianate village of Portmeirion, is run by the Snowdon Mountain Railway company who lease it from the National Park.

Alan Kendall, from the railway company, said the new building offered "a much better visitor experience".

"It improves the quality of the experience for all visitors," he said.

"Even when you are in the building, you have a view of the summit and a panoramic view of what's going on outside, as opposed to what you have at the minute, which is a bunker providing shelter and little else."

Conservationists say they want great care taken to ensure any new building does not detract from the beauty of the mountain.

Prince Charles has refused to comment on the new plans

Rob Owen, policy director for the Snowdonia Society, said it was vital to ensure any building met "all the needs of the locality".

He said the new proposals were an improvement on the current cafe, which was built in 1936, but he was keen for several considerations to be taken into account.

"Local products need to be used in building work," he said.

"And sunlight reflecting off the metal and glass must be kept to a minimum so that, from a distance, you wouldn't even know it's there," he said.

Plans to revamp the cafe have been running for years.

In 1997, a survey in the Snowdon area found more than 75% of people questioned thought the cafe building should be replaced.

And, in June 2002, the redesign scheme was unanimously approved by members of the Snowdonia National Park Authority.