Bold visions for the development of Whitlingham Country Park include everything from a spa and open air theatre to water lodges built on stilts around a new lake.

Other elements of plans which have gone on public display in the flint barn visitor centre of the leisure attraction on the doorstep of Norwich include an equestrian centre, boutique hotel, fitness and mountain bike trails and a range of camping facilities, from a humble tent site to timber pods and even tree houses.

The Crown Point Estate, run by the Colman family, invited architects to come up with their personal visions for the beauty spot, focusing on the former Lafarge gravel works site opposite the visitor centre which has only been re-landscaped in the past year.

Out of seven original applicants, the plans of three Norwich-based architects' firms - Feilden and Mawson, Hudson and LSI - have now been shortlisted by a panel including representatives of the estate, Whitlingham Charitable Trust and the Broads Authority (BA).

Estate spokesman James Colman said: 'With the gravel working finished, the question was raised of what to do with the land which is owned by the estate, and we started talking to the Broads Authority and Whitlingham Charitable Trust to find a solution.

'This is still a vision in progress and that is why we are keen to receive feedback from the public on the three sets of plans.'

Mr Colman said the park had evolved significantly over the past 15 years and now, with more than 400,000 annual visitors, there was a need for improved education, catering and toilet facilities which could be incorporated in any new development.

Visitor numbers were likely to increase further in the wake of other significant plans in the city, such as the development of the Deal ground.

Mr Colman said the architects' visions would now be scrutinised to test their viability and a decision on which plan to follow - made in consultation with the BA and trust - was likely to be taken in the autumn.

It is hoped that plans can be submitted to the BA by the spring of next year.

The exhibition of plans, organised by La Ronde Wright planning consultants, will be open until July 18.

Feedback forms, available at the flint barn, may be placed in the box at the exhibition or sent to La Ronde Wright at 4, The Close, Norwich, NR1 4DH.

Feilden and Mawson architect Stuart Jones said their vision had been inspired by the peace of the site which had been used as a retreat by the Priors of Norwich.

They were proposing a 'gateway' building which could either be a spa or a classical music venue with a restaurant/cafe complementing the existing offer.

Their plans also included an outdoor activities centre with such attractions as a high-level rope walk, fitness trails, mountain biking, horse riding facilities and a natural swimming pool.

The development would also include a courtyard for cafes, exhibition spaces and workshops.

Mr Jones said: 'The tourist trade is important and we are proposing three tiers of accommodation, sustainable timber pods built half into the ground, beach hut-style buildings for 'glamping' and wild camping.'

He said their vision was for 'zero carbon holidays' where people could leave their cars behind.

Robin Hudson, of Hudson Architects, said his vision was to build on the country park's existing varied activities and to nurture 'the personal relationship between individuals and nature which you feel has been lost'.

His plans would see the visitor centre expanding to become a 'real centre for the park'.

In addition to a restaurant with a training kitchen, there would be retail outlets and bike hire.

Car parking would be moved away from the broad to a new screened location, making a much better setting for the barn.

His design would see a conference centre on the old quarry site, an accommodation building for backpackers, an innovative campsite with such features as upmarket shepherd's huts, an equestrian centre and an events field.

Mr Hudson wants the natural setting enhanced with community orchards and wildlife-friendly planting, country craft activities such as den-making and a bee centre.

David Thompson, of LSI Architects, said they were proposing a landscape-led scheme taking advantage of the seclusion of the site.

'Our starting point was how could sustainable tourism take advantage of this asset,' he said.

'And how could we achieve a critical mass of activities that could be self-sustaining and contribute to the overall maintenance of the park.'

His plans include a boutique hotel with fine dining and an amphitheatre bowl for open air theatre.

A range of camping facilities would include everything from eco-lodges and tree houses to water lodges built on stilts in a new lake.