CHAMPAGNE BAR AT COUNTRY Appointed with a marble bar and leather furnishings, this sophisticated alcove is on the second floor of Geoffrey Zakarian's new restaurant in the Carlton Hotel. It offers more than 40 Champagnes and sparkling wines by the bottle, a handful by the glass and a list of Champagne cocktails. Soon it will become a prelude to dinner in the grand second-floor dining room, which is to open in a month or so: 90 Madison Avenue (29th Street), (212) 889-7100.