Position rack in center of oven and preheat to 325 degrees F. Butter 10-inch-diameter springform pan with 2 1/2-inch-high sides. Line bottom of pan with waxed paper. Butter waxed paper. Wrap outside of pan with foil.
Using electric mixer, beat cream cheese and sugar in large bowl until smooth. Mix in orange peel and vanilla. At low speed beat in whole eggs 1 at a time, stopping to scrape down sides of bowl frequently. Using clean dry beaters, beat egg whites in another large bowl to soft peaks. Fold whites into cheese mixture in 2 additions.
Transfer batter to prepared pan. Set cake pan into large baking pan. Pour enough hot water into baking pan to come 1/2-inch up sides of cake pan. Bake until cake is light brown on top and tester inserted in center comes out clean, about 1 hour 10 minutes. Transfer cake to rack and cool 15 minutes. Using small sharp knife, cut around sides of pan to loosen cake. Release pan sides and cool cake completely. Cover and refrigerate cake overnight.
Let cake stand at room temperature 1 hour. Remove peel and white pith from oranges. Using small sharp knife, cut between membranes of oranges to release segments. Pat orange segments dry with paper towels. Place orange segments decoratively around top edge of cake. Garnish with mint leaves.
