Top cities for millionaire second homes

When we think of second homes for the leisure class, we usually think Hamptons, Cannes or Palm Beach.

But today's globe-trotting, business-minded, city-seeking rich are more likely to want pied-à-terres than beach homes as their second homes. According to a new study from New World Wealth, a wealth research firm, London is the top second-home hot spot for the world's multimillionaires.

The study found that there are 22,300 multimillionaires—or those worth $10 million or more—who own second homes in London. That's in addition to the 9,700 multimillionaires who have primary residences in London.

Read MoreFlorida mansion listed at $139M

"During peak holiday months, London can be home to up to 32,000 multimillionaires in total," the report said.

The study found that the bulk of second-home buyers in London come from the rest of the U.K., as well as Europe. "There are also substantial numbers from China, India, Russia and the Middle East."

Ranking second is New York City, with 17,400 second-home multimillionaires. The study said New York's second-home owning rich are mainly from the rest of the U.S., despite all the media attention around foreign buyers in Manhattan.

Read MoreMost expensive house (we could get into): Beverly Hills

Hong Kong is third with 14,800 and Singapore is fourth, with 11,200.

The more traditional beach retreats ranked further down. The Hamptons ranked sixth, with 7,800. And Palm Beach, once a required destination for the American elite and European aristocrats, was a distant 13th, with 3,400.

Some other notable hot spots with at least 1,000 rich second-home owners include Las Vegas; Aspen, Colorado; Pebble Beach, California; San Diego; Lake Como, Italy; Cannes, France; and St. Tropez, France.

Read MoreFor $99,000 a week, this London rental is yours

—By CNBC's Robert Frank.