Home improvement is all the rage today. But more-affluent homeowners aren't stopping at a revamped kitchen or a bigger master bathroom — not by a long shot. A certain slice of the population is going big, even extreme: Think bowling alleys, climbing walls and game rooms you'd pay to be invited into.

"I think what people are doing, they're really adding to their homes in the ways they had dreamed their homes to be," says Juliana Catlin of Catlin Interiors in Jacksonville, Fla. and a past national president of the American Society of Interior Designers.

The dollars spent by affluent homeowners on renovation are driving the remodel market nationwide, according to a 2005 report by Harvard University's Joint Center for Housing Studies. The highest-income homeowners spent three times the amount on remodeling than the median-income homeowners, the study found.

Take a break from your modest carpet samples and faucet catalogs and check out some of these wild home improvements.

Got a spare 90 feet? Install a bowling alley
"Residential installs have picked up over the last four years about 200%; it's incredible right now,” says Tim Claxton, sales manager of United Bowling, a 32-year-old bowling alley construction company in Amelia Island, Fla. "We did 18 private homes last year," says Claxton, including a recent job at the $15 million home of a Warner Bros. executive. "We get requests daily. We have to weed out who's serious and who's not," he says, estimating that private homes are now about half of the company's business.

Price: $88,000 gets you two regulation lanes, installed, with the whole enchilada: pins, pin-setting equipment, wood lanes, computer scoring — even shoes!

What's your home worth?

Fire when ready (even in your P.J.s)
How about a home firing range? That Warner Bros. executive who installed the bowling alley had one. "We don't seek that market out, but it finds us — and the rate at which it finds us is growing," says Mitch Petrie, director of law enforcement and commercial sale for Minneapolis-based Range Systems, which manufactures and installs range equipment for law enforcement and the government. "It's a real market."

"They're pretty normal guys — businessmen, doctors," Petrie says of his civilian clientele. "We've got, on Long Island, a dentist; an entrepreneur in Naples, Florida who's got one in his vacation home; a scientist in the Las Vegas area; and a large general contractor in the Las Vegas area has probably a $50,000 range in his home." Costs can skyrocket, he says, as shooters invest in special ventilations systems and interactive video shooting simulators like those used by police.

One potential obstacle for homeowners: Many municipalities don't allow discharge of firearms within city limits.

Price: "$10,000 buys you a basic full-wall bullet trap system, and a cable-operated target system with some ceiling protection, as well," says Petrie. That doesn't include all ventilation or full protection from noise, however.

Climbing the walls
How about your own in-house rock-climbing wall? "It is something that we do a little bit of," says Cort Gariepy, designer for Barre, Mass.-based Rockwerx, which makes rock-climbing walls. "It's usually these multi-million dollar places that are more of a compound," says Gariepy. "We've got one on the books for out in Las Vegas. It's probably a $50 million home, and it will have a $75,000 rock wall in it — and it will actually not be in the house, but in the pool house.

"It's really something just for their kids," Gariepy adds. "Most climbing enthusiasts don't have the money to pull this off. Most of these things tend to be the things people want just to say they have it."

One genuine climber who wanted one is Don Mealing. Mealing, 46, and his wife are passionate rock climbers. "We both have done a lot of climbing at Yosemite over the years," he says. So when they thought of their 12,000 square-foot dream house, called "Cloud's Rest" at 9,000 feet at the top of The Canyons ski resort in Utah, they knew they wanted to have a climbing wall incorporated into the design of the home, which will be finished in June.

Some wall — it's about 32 feet high with about 14 climbing routes on it and six difficult "crack" routes. Glass windows surround the wall on three sides, so that skiers riding by on the chairlift will be able to see climbers inside, says Mealing.

"Not only is it really functional, it's really beautiful, too," he says of the wall, which is made by Boulder, Colo.'s Eldorado Wall of a concrete-like substance the company calls Dudetex.

Price: For state-of-the art walls like those built by Rockwerx and Eldorado Wall, price is kind of a moot point. "Most people, if they've got a cathedral ceiling, it might be 16 or 18 feet high. And that's not enough to do something with," says Rockwerx' Gariepy. "You need 25 to 30 feet — that's a good starting point."

Of course, many climbing addicts build (or have built for them) cheaper, simpler bouldering walls in their homes out of two-by-fours, plywood, heavy screws and climbing holds. Costs can range hugely, but expect to pay $5,000 to have a contractor build a home gym that's large enough to cover a few walls of a room and that will keep you entertained, says one former wall builder. (Climbing holds alone cost $3 to $9 each.) A lot of information about building your own wall is available on the Internet: See IndoorClimbing and MetoliusClimbing.

Rise of the wine cellar
Even people who don't drink much vino are adding wine cellars to their homes today — and not just some side cabinet to hold a few bottles of Two-Buck Chuck.

How expensive will the cellars get?

"I'm not sure you can put a cap on it yet," says Jack Diener, sales director for Cincinnatti-based Wine Cellar Innovations.

An interesting shift is that the wine racks are becoming secondary to the design, says Diener. Some of the cellars have "ridiculous amounts of custom millwork" — hand-carved moldings, panels and beams and anything else that makes the cellar look very unique and old world.

One year ago, when the couple more than doubled the size of their Seattle rambler, they installed a 7-by-15-foot pool from Pennsylvania-based Endless Pools.

The mini-pool, which can be installed in a deck or sunk into a floor as Hammarlund and Peterson did, has an adjustable current that keeps a swimmer in place while he or she swims for exercise.

The verdict? Two (water-wrinkled) thumbs up. "You can swim anytime you want, and keep the chlorine levels down really low," says Hammarlund, who says he now swims about 10 times a week in the pool, which he keeps at 84 degrees. "We haven't had any trouble with the humidity — that was our architect's main concern," he adds.

"I think the endless pool is really best for people who have figured out how to swim well," Peterson says, "it's not a place to hang out," like a hot tub.

"The only drawback," she adds, "is that now I don't have any excuses for not exercising."

Price: About $19,400 for the standard package.

Hoop it up
A basketball hoop hardly sounds lavish — everybody has one in front of his house. But how about an entire basketball court?

"We're in the middle of doing some drawings for a basketball court that's underground," says Ben White, vice president of Evanston, Ill.-based Benvenuti and Stein, which does high-end residential new construction and remodeling. Subterranean hoops? A court has to be at least 25 feet tall to accommodate shots, explains White, but zoning issues and trusses for the structure mean that burying much of the building is the best answer. The court will be accompanied by a little clubhouse for the owner to hang out in and play cards, says White; underneath the poker house is the exercise room, from which a player can walk onto the court. "There's the potential that we will do a tunnel eight feet tall" to the house, he adds, so that the owners' children don't have to go outside during the Chicago area's bitter-cold winters.

"Nutty stuff," he says.

Price: If you have to ask …

Creating the ultimate game and hobby rooms
For many homeowners, the day of the half-finished basement with a pool table in it is long gone, says interior designer Catlin. "We designed a game room for a man that was over 2,400 square feet — it had shuffleboard, the kind of thing that was usually located in a bar; professional-level dart board; pinball, which he remembered from his days in college; and we got a pool table and large-screen TV; and there was an exercise room off that room," she recalls. "The male's dream room," Catlin calls it. Oh, yeah, there was also a bar.

"They're also gilding the lily on the finishing touches," Catlin says of additions like these — adding old-wood finishes from an antique barn, say, or full sound systems and "smart house" technology that lets people see who's at the front door while they're playing Texas Hold 'Em at their special poker table. In short, "It's not just about square footage."

Why such elaborate additions? "There's a term called 'the wombing of America,'" Catlin says. "I think people have traveled less, and I think there's a direct correlation with wanting to have full relaxation after a hard day's work without the feeling of have to get away."

Indeed, says the American Society for Interior Designers, specialty rooms are hot. Some women today want whole rooms where they can knit, scrapbook or sew — and store those items, says Catlin — while more men are asking for rooms specifically dedicated to, say, their hunting supplies and gear. "I think the baby boomers, as they're entering their last 10 or 15 years in the workforce, they want rooms that are outfitted for them,” she says. "We kind of laugh and call them the ultimate hobby rooms. And they don't put them together — there's a His and a Hers."

Price: A game room or hobby room can get as costly as you want, but the one Catlin designed for that customer cost "close to $400 a foot, probably," she says. "People will make a million-dollar addition to play out their personal dream home."