The awards which highlight how good design has a positive effect on the environment, had 11 entries this year.
Judges loved the way College Lake Nature Reserve on Upper Icknield Way fits into the landscape.
Its sloping grass roof and surrounding planting up to the glass doors makes it almost invisible plus there’s a horn of a prehistoric mammoth, which was found on the site, set into the floor under glass.
The centre, which is run by the Berks, Bucks and Oxon Wildlife Trust, has spectacular views of the lake as well.
Head of conservation and education Christopher Williams said: “Anyone who appreciates well-designed buildings, tasty cakes and the chance to enjoy a wide range of wildlife should definitely add College Lake to their list of places to visit this autumn.”
The Old Brewery House in Ivinghoe was commended but the overall winner was a Georgian-style country home called Horseshoe Hill House.
The annual awards are held jointly by The Chiltern Society and Chiltern Conservation Board.