The vast U.S. Embassy that dominates London’s Grosvenor Square is either a modernist masterpiece by Finnish-American architect Eero Saarinen or an egregious monstrosity, depending on your point of view. Owing to security concerns, the embassy will move shortly to a purpose-built, fortified complex on the South Bank of the Thames. And its former home is to become a 137-room Rosewood Hotel. To the disappointment of some, the Grade II-listed façade cannot be altered. Even the giant gilded bald eagle, with its 35-foot wingspan, will continue to glare down from the roof.