Ruddle Wilkinson has been chosen to masterplan a project worth up to £750 million on Liverpool's Garden Festival site - including a 79-storey theme park.
The scheme will include a marina, a sports stadium for up to 40,000 people, a 3000-bed hotel and a 3000-seat conference arena within the tower, which could become Europe's tallest.
Norman Taylor, managing director of the Peterborough-based practice, said: 'We have been trying to get our minds round the size of the project. We don't know exactly what our role will be in the long term. We have to develop concepts for the site and see what is feasible.' The architect is expected to complete a feasibility study around October and present it to the council and business leaders.
Initial proposals for the vertical theme park included a 30-storey watel. Ruddle Wilkinson is to be briefed in a few weeks and Taylor could not comment on final proposals. 'We will look at what's realistic and what can be achieved.'
A spokesman for the developer, Wiggins Group, said an outline planning application was expected around the year's end. It would decide after the feasibility study which, if any, elements went out to competition.
Wiggins Group said it wanted to create a landmark design in the tradition of Pugin, Scott and Gibberd.
First it has to clear around 10 million tonnes of rubbish buried on the 37ha site. The land was used as a rubbish dump before the garden festival in 1984. Decontamination will cost around £30 million and involve neutralising explosive landfill gas.