Where indoors meets outdoors, and too much is not enough

New York

TWENTY-foot-wide (6m-wide) glass walls retract electronically at the tap of a cellphone app at the over-the-top US$39.5 million furnished mansion John Kean built last year on 4 acres (16,187 sq m) in Southampton, New York. They disappear into wall pockets, blurring the distinction between indoors and out.

The living room, with its full bar, dovetails with an outdoor covered terrace lengthy enough for a banquet table for 75 guests.

"You come to the Hamptons to be outside," Mr Kean said of his 15,500-square-foot, 10-bedroom, 12 full and three half-bath mansion.

Another tap and a mesh screen comes down, enclosing the terrace and turning…