Every kitty needs a castle of his own and doting cat fanciers seem more than willing to oblige their feline friends.

Take Bob Walker, for example. Walker and his wife Frances Mooney let their imaginations run wild when they began remodeling their modest single-story home into what many people regard as the ultimate cat house.

In fact, Walker has gained attention among pet owners by documenting his home's massive transformation in a series of colorful photos that were published in book form as "The Cat House."

"What began as a simple floor-to-ceiling scratching post to prevent our nine cats from sharpening their claws on the furniture is now a series of ramps, stairs and catwalks that crisscross our house," explains Walker, who resides in San Diego, California.

"To accent the playfulness of our home's 1,500-square-foot interior, we painted the tunnels and terraces in more than 40 vivid colors, providing a backdrop for my wife's collection of Mexican figurines and toys," says Walker. "While my book was never meant to be a blueprint for do-it-yourselfers, it does offer basic ideas for designing ramps and mouse holes that allow cats to pass from room to room."

Walker began building his 140-foot maze of overhead staircases and peep holes more than 10 years ago and regards it as a work in progress. Walker and Mooney tackled most of the construction work on their own, using fresh lumber, heavy-duty hemp and cast-off wooden boxes. Then, they color coordinated the entire project in explosive shades of the rainbow - ranging from radiant purple and peacock blue to firecracker red and sunburst yellow.

During the past decade, they've invested more than $10,000 in creating a kitty-sized playground, and their current brood of 11 cats seems to appreciate the effort. Throughout the day, they're a blur of hyped-up cat energy as they dart into tunnels, bolt down a curved staircase or crawl into cozy niches for a quick catnap. Even the bathtub, beds and bookshelves have become part of their playground.

For anyone planning to add cat-friendly fixtures to their home, Walker offers a worthwhile suggestion: Install ramps away from curtains and walls.

Most cats, he says, will tear your curtains to ribbons if they can reach them, and plump cats need extra room to turn around.

Walker's book on feline architecture has apparently inspired other cat fanciers to follow suit, even those who live more than an ocean away.

In Japan, the Tokyu Hands department store in Tokyo's Ikeburkuro district has transformed its eighth floor into Nekobukuro - a playground for cats that bears striking similarities to Walker's West Coast home.

The store's climate-controlled showroom is decked out with brightly colored wall murals, scratching posts, overhead planks, a Hello Kitty-shaped television and a 10-foot-long case designed to look like a subway car.

Customers pay $5.50 (600 yen) to interact with the store's collection of 20 free-roaming cats. Among them are a hairless Sphinx, a Scottish Fold, Bengal kittens and an American shorthair silver tabby.

Nekobukuro is becoming a popular dating spot for young people and would-be cat owners, notes American travel writer Jennifer O'Bryan.

"In a megapolis like Tokyo, where real estate is precious, renting a house or apartment that will allow pets is always a challenge," explains O'Bryan. "But even for those who live in a place where pets are allowed, long commutes and even longer days at the office make it almost impossible for most single people to look after a dog or cat on their own."

Pet-deprived residents in Japan pay $5.50 each to play with purebred cats at Nekobukuro, a popular Tokyo pet store.

Fortunately, Oahu residents can enjoy the company of a furry companion closer to home by visiting the Hawaiian Humane Society, located at 2700 Waialae Ave.

"On any given day, our walk-in cat hale has 20 to 30 cats and kittens available for adoption, and people can interact with them for free," says Kawehi Yim, the Society's director of Community Relations.

If you're already a cat owner, log on to www.hawaiianhumane.org to discover ways of making your home more pet friendly without major remodeling. For example:

• Prevent your indoor cat from feeling confined by installing a prefabricated kitty condo or climbing tree. Tall models make use of vertical space and add to a cat's sense of adventure.
• Offer your cat opportunities to look outside by attaching simple perches or shelves near windows. If possible, place bird feeders near windows to attract wildlife that your cat will enjoy watching.
• Leave windows open so your cat can enjoy plenty of fresh air. Make sure all window screens are fastened securely, especially if you live higher than the ground floor of a home or apartment.
• Hide cat toys at various places in your house. Curious cats will enjoy hunting for them throughout the day.
• Leave empty cardboard boxes or "cocoons" on the floor of your bedroom, bathroom or kitchen. Cats are amused by playing hide-and-seek.

For more tips on do-it-yourself cat projects, visit Hardware Hawaii Ace, Home Depot, Lowe's or City Mill. HS