The wet lounge at the Peninsula Spa by ESPA.   (Photo: Courtesy of The Peninsula Spa by ESPA)

The Peninsula Spa by ESPA
700 Fifth Ave., 21st fl., at 55th St.; 212-903-3910
After a yearlong renovation, this opulent twelve-room spa reopened in January 2009. In addition to an extensive treatment menu, there's a pre-treatment tea lounge, aromatherapy steam rooms and saunas in each changing room, and a post-service lounge featuring plush, semi-private beds and a spread of snacks. Bonus: Book treatments for two hours or more and gain access to the 42-foot pool and fitness center with sweeping views of Manhattan.

Caudalie Vinothérapie Spa at the Plaza
1 W. 58th St., fourth fl., at Fifth Ave.; 212-265-3182
Wine-inspired brand Caudalie brought its vinotherapy concept to the Plaza in January 2009. In addition to wine-themed treatments—Crushed Cabernet Scrub, Fresh Grape Massage—there's a hammam steam room and a relaxation lounge pouring Grand Cru Château Smith Haute Lafitte.

The Spa at Mandarin Oriental
80 Columbus Cir., 35th fl., at 60th St.; 212-805-8880
The 35th-floor spa, with its floor-to-ceiling windows framing Central Park, includes a unisex Tea Lounge, corridors of treatment rooms, and sex-specific plunge pools. The services incorporate a dash of the Far East, too: Ayurvedic skin and body treatments, and Ama-Releasing Abhyanga and Lomi-Lomi massages are standouts.

Sense Spa at the Carlyle
35 E. 76th St., third fl., at Madison Ave.; 212-744-1600
Like the Carlyle Hotel that houses it, this decadent spa is a sanctuary of understated glamour, and the services match the opulent décor. In addition to decadent scrubs and facials, body treatments incorporate Red Flower products and natural ingredients like Moroccan tea and rosemary, followed by a rinse in a luxurious rain shower.

Shibui Spa at the Greenwich Hotel
377 Greenwich St., nr. Franklin St.; 212-941-8900
The dazzling design alone is enough to recommend this decadent Asian-themed spot inside the Greenwich Hotel. A painstakingly reconstructed 250-year-old Japanese farmhouse frames the pool and lounge area, and one of the spa's four treatment rooms houses a tub for Japanese bathing rituals.