They range from Hong Kong's 118-story International Commerce Center, home to a penthouse infinity pool and one of the world's highest hotels, to the slightly taller Shanghai World Financial Center, which is known as "the bottle opener" for the trapezoidal gap at the top.

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Mr. Boros added a penthouse apartment with a roof garden and pool.

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The two-floor, 22, 000-square-foot space may be situated in the heart of stuffy and conservative Fifth Avenue, but the spa is daring to go where few, if any, have gone before: A Watsu pool (for underwater shiatsu massage) and a penthouse roof garden for outdoor massages in good weather are two of Cornelia's unique offerings.

FORBES

James Stanley, a New York-based designer, says he recently did a pop-art-themed penthouse for a wealthy bachelor in Manhattan that has a flame-red living room with foosball and pool tables and a "Star Wars"-themed bedroom room.

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