Grosvenor Square is being recast for a new era, with the former U.S. Embassy transformed into a Qatari-owned luxury hotel and F.D.R.’s square into a haven of biodiversity.Grosvenor Square is being recast for a new era, with the former U.S. Embassy transformed into a Qatari-owned luxury hotel and F.D.R.’s square into a haven of biodiversity.