As the son of legendary hairstylist Vidal, Elan Sassoon was practically predestined to open Mizu, his new 3,300-square-foot salon in the Mandarin Oriental hotel. The sculptural ground-floor space just off Newbury Street, with its vaulted ceilings and pale-gold laser-cut partitions, recalls his father's love of bold architectural shapes. To keep jet-setting clientele happy during chair time with creative director Patrick McGinley, Elan offers preprogrammed iPods, mini televisions, and wireless laptops; a private staircase whisks overstressed types upstairs to the hotel's Zen spa. Frequent fliers take note: A second Mizu location opens this month in Manhattan.