Euan Hall, chief executive of the Land Trust which ran the competition, said:
"Michael displayed a strong empathy with the site and the Trust’s ambitions.
"He brought a compelling and thought-provoking ideology to the table and his ability to consider the built and open environments impressed us."
The winner was chosen after interviews with Hall and co-organiser RIBA Competitions. Michael Lee Architects will now firm up design ideas.
The design team also includes Mike Wells of BioDiversity by Design, an ecology practice based in Bath.
A representative said said:
"Apart from a little woodland and three chimneys, the site is bare.
"Land Trust wants the land to self-generate income so this could mean an eco-hotel, visitor centre or some other form of architecture.
"Landscape will play a large part, with more woodlands and paths, green gyms, BMX parks, ranger services and camping."
Dates for work to start depend on the planning application and funding strategies.