(FORTUNE Magazine) – PAUL ALLEN

The Microsoft billionaire probably doesn't miss land much when he takes to the sea in his yacht. The 413-foot Octopus comes equipped with its own speedboat, a personal submarine, a recording studio, a movie theater, two helicopter pads (one doubles as a basketball court), and a glass bottom to view sea creatures.

MICHAEL STEINHARDT

The illustrious hedge fund manager has a wildlife park on his 51-acre estate in Bedford, N.Y. Among the animals he keeps there: kangaroos, camels, zebras, ostriches, wallabies, antelopes, and monkeys.

STEVEN SPIELBERG

One plan for the movie executive's Brentwood horse-riding ring called for a 27,000-square-foot building with a retractable roof, but the neighbors objected. Spielberg ended up building something much more modest: an outdoor ring on nearly three acres of land.

RICHARD GARRIOTT

The videogame mogul doesn't just create fantasy; he lives it. His 5,000-square-foot home in Austin has secret passageways, revolving bookcases, and a dungeon. But wait! Next up is a 25,000-square-foot castle, complete with all the fixings. Moats, drawbridges, dungeons, rotating walls, secret passageways, a room that doubles as an elevator, and a master bedroom with a ceiling that opens to the stars. The home will also have a swimming pool with underwater tunnels.

JAKE BURTON

The founder and chairman of Burton Snowboards is an athlete for all seasons. His Vermont home has an indoor soccer court and an outdoor mini-halfpipe for summer skateboarding, as well as a mountain-biking run with tabletop jumps. Each winter the outdoor hockey rink is iced over, and snowboarding rails are erected throughout the yard.

DAVID SIEGEL

The time-share king is two years into building his 90,000-square-foot Florida palace named Versailles. The home will have an indoor hockey rink with its own Zamboni, four swimming pools (one Olympic-sized), a health spa with massage rooms, a stadium tennis court seating 200 spectators, a full-sized baseball diamond, and a two-lane bowling alley. -- Ellen Florian Kratz