Istanbul’s trendy Ni?anta?? neighborhood is a cultural hub pulsing with energy and glamour. At the center of the action is the new St. Regis Istanbul (stregis.com), a contemporary haven that opened in April near Maçka Democracy Park. The hotel’s 136 guest rooms and suites—which include a two-bedroom Presidential Suite and the sleek Bentley Suite—feature a bold blend of bronze, marble, leather, and wood. Many rooms afford views of the park and of the&n…