Paul Allen's development of South Lake Union, with at least a dozen new buildings devoted to high-tech enterprises and grandiose plans to become a highrise virtual downtown, extends uphill and eastward to encompass the residential neighborhood known as Cascade. REI built its headquarters here and surrounded it with a lovely garden; the grand old St. Spiridon orthodox church stands guard over a street of new construction. One facade of Alley 24 remains untouched; the......