After a global search spanning six continents, Forbes has put together their list of the World's Most Expensive Homes for 2007. $100 million will get you more in - for example - South Africa than it will in New York, but the international ultra-luxury market is growing so fast, say real estate agents who deal with clients in the market for such homes, that the price gap is diminishing and soon all of these houses could be closer to the high-end of the pricing spectrum and a list like this one might look very different in 5 years. For now, top priced homes (in USD) include:

• Updown Court in Windlesham, Surrey ($138 million) is a 103-room home on 58 acres of lush grounds, with an indoor squash court, bowling alley, 50-seat cinema, helipads and a heated marble driveway.
• Hala Ranch in Aspen, Colo. ( $135 million, pictured) has 95-acres and a 56,000-sq. ft. mansion, with multiple outbuildings and guest houses, stables, a tennis court and an indoor swimming pool.
• Waterfront Estate in Istanbul, Turkey ($100 million) is on only .75 acres of land, but has 30,000 square feet of ultra-luxe space divided into 64 rooms, most of which look out onto the water.

Check out the full list for further details and the rest of the top priced homes.

Free online real estate estimates, such as the Zestimates provided by Zillow.com, are a boon to many home buyers. They provide fast, hassle-free estimates of homes all over, with the intention of giving shoppers an idea of what's available before they even head out to look in person. According to the Wall Street Journal, however, Zillow isn't quite as reliable as it seems to be, given the fact that it gives prices down to the dollar, not just round-number estimates. For instance, it listed a 7,600-sq. ft. home in Fall City, WA at $661,756, but the home sold in January for over $2.5 million. The Northbrook, Il. house pictured was pegged at $450,000, but sold for nearly double. And the errors can go the other way, as well, with an El Cerrito, CA house selling for $80,000, though its estimate was over $500,000.

Zillow tries to keep things as accurate as possible, of course, but the bottom line is that it is best to take their estimates with more than a grain of salt just in case the 5% error you are expecting turns out to be 50%.

Forbes Magazine just released their picks of the most expensive homes in the US for 2006. The real estate market may be slowing somewhat, but that fact didn't stop the average price of a home on this list from jumping up to $71 million from $58 million. In a change from last year's list, the $75 million asking price of the top home from 2005 - the Three Ponds, in Bridgehampton - was surpassed by two houses: Donald Trump's Maison de L'Amitie in Florida, with an asking price of $125 million, and the Portabello Estate in California, also listed at $75 million. Other picks include Martin Zweig's apartment and a limestone mansion in San Francisco.

A marketing director in Santa Clarita, California has a new take on how to sell a house. To give the houses in a new development a "lived-in" feel, she has hired a group of actors to play house while prospective buyers come out and tour the property. "Mom," "Dad" and their two "kids" bake scones, celebrate a birthday party and play games, interacting with each other and with any guests who wish to play along or ask questions. It's "reality" real estate and the program has been dubbed "Home Life." Many of the guests who toured the house when it opened were actual realtors, not looking to buy the house, but to see how appealing having a "family" would be to clients.

As one visitor from USC's business school put it, "You imagine yourself in this situation. If you have a beautiful experience, that gets people to think, oh, I want to live like that!" The model family was as appealing, if not more so, than the home itself. It's easy to see how clients, perhaps used to watching reality shows on television, could relate quickly to a similar scenario that confronts them in real life.

Since the setup had immediate appeal to buyers and realtors alike. This could be the start of a new real estate trend, particularly with upmarket estates and in new developments, where houses might look less lived in because of their newness or their size.