Forbes.com has compiled the first comprehensive list of the priciest residences on the planet—the top five per continent, excluding Antarctica, to be precise. We combed through thousands of property listings, compared hundreds of homes and contacted dozens of brokers and owners in our quest. Here's what we found:

They are large enough to contain entire neighborhoods, and yet not as large as you might expect. They are astoundingly expensive and, in some parts of the world at least, surprisingly cheap. They are lavish and gold-trimmed, modest and wood-sided, and perched on handkerchiefs of land and large private islands.

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The most expensive home in the world was no secret: an infamously lavish new estate in England known as Updown Court. The 103-room mansion is set on 58 acres in the wealthy London suburb of Surrey. It has five swimming pools and every possible trimming, and it just hit the market this year. The least expensive on our list was a $5 million house in São Paolo, Brazil, a vintage residence that needs some updating.

Expensive homes tended to be concentrated in particular areas. South Africa dominated the Africa list, for example, and Brazil had the bulk of the most expensive South American properties. The U.S. listings were, unsurprisingly, in rich areas such as New York State and California. Overall, the most expensive homes were in the U.S., U.K. and France. Other places could hardly compare.

That Britain was so expensive doesn't surprise Trevor Abrahmsohn, founder of Glentree Estates in London and broker for the second-priciest home in Europe.

"As far as property is concerned, London is probably is the capital of the world," he says. "It straddles Eastern Europe as well as the Americas and Europe."

The owners of the U.S. properties tended to be American citizens with gobs of cash to spare. For example, financier Martin Zweig, who owns the most expensive condo in the U.S., a $70 million penthouse atop New York City's Pierre hotel. But in London, the pool of high-end buyers is far more international, says Abrahmsohn. He's in a position to know, having sold a house to steel tycoon Lakshmi Mittal, who last year set a world record for a residential sale when he purchased a London mansion for $100 million.

"London is the epicenter of the international cognoscenti," Abrahmsohn says. "Since the 1970s, I've seen every nationality. Every time there's a hike in oil prices, every time there is a political uprising, all the wealthy refugees come to the U.K., and they buy super-luxury property."

They buy because values increase, and they won't see their assets dissolve in a currency crisis or be confiscated by a rogue government.

Not to mention "it enhances their status," Abrahmsohn adds.

At the other end of the price spectrum, brokers in South Africa argue that property is undervalued, and there are some serious bargains for international shoppers. There, the most expensive real estate tends to be game lodges or wine estates, bought by rich businessmen as retreats.

"Property prices have more than doubled in the last few years," says Jan Lindeque, a broker with South African real estate agency Engel & Voelkers. "Still, if you compare the house for $4 million in Mallorca and you look for a similar house here, it's much less expensive. You get much more value for the money."

The World's Top Five
1. Windlesham, England $122.2 million
2. Bridgehampton, N.Y. $75 million
3. New York, N.Y. $70 million
4. Malibu, Calif. $65 million
5. London, England $61.1 million

In fact, we were hard-pressed to find homes outside of Europe and North America that were priced over $5 million, though South Africa has some very impressive mansions on the market. Very, very few people are rich enough to buy a multimillion-dollar property, though in places such as South Africa and China the ranks of the wealthy are growing.

"There are a lot of people that are getting very rich very fast," Lindeque says.

A few caveats about our list: There may be other properties out there that are expensive enough to have made it. But we didn't include magnificent homes that are "unofficially" on the market and only being shopped around to selected potential buyers.

We did not include a property if we could not confirm its price, or if it was not yet finished. A $60 million home in Beverly Hills, Calif., didn't make the list, because it is only 85% complete.

We left out developments, resorts, land and agricultural properties, though we did make some exceptions to the latter. In Argentina and South Africa, for example, estates that include some grape growing or ranching draw affluent buyers looking for country retreats. Had we included U.S. ranches, Little Jenny Ranch, near Jackson Hole, Wyo., would have just made our North America list.

Finally, our price estimates are based on exchange rates in July 2005. Currency fluctuations can certainly change the rankings.