Castello di Amorosa - Word to the wise: Imbibe the cabernet sauvignon and pinot grigio at the Castello di Amorosa winery carefully, because somewhere in the 121,000-square-foot, 107-room, eight-level complex there's a dungeon with a functional Renaissance-era iron maiden. It took 14 years to construct the castle using historically accurate medieval building techniques. The end result is an "authentic" 12th- and 13th-century Tuscan castle with drawbridge and moat.

Hearst Castle - Understatement of the millennium: William Randolph Hearst's 1919 directive to architect Julia Morgan to "build a little something" on his ranch in San Simeon. Then again, a 115-room "Casa Grande" inspired by a Spanish cathedral is a relatively modest proposition compared to the 250,000 acres and the 13 miles of coastline it's set on.

Bishop's Palace - Of all the Gilded Age Victorians built by Nicholas Clayton along Galveston's Gulf Coast, the Bishop's Palace (née Gresham Castle, 1893, after its original owner, Santa Fe railroad magnate Walther Gresham) remains the grandest—and not just because its steel and stone hulk survived the Great Storm of 1900.

Boldt Castle - hat do you do when you come across a heart-shaped isle while vacationing with your wife in the Thousand Islands? If you're upstart industrialist George Boldt, you buy it and hire 300 stonemasons, carpenters, and artists to build a six-story, 120-room testament to your love.

Castle in the Clouds - Location, location, location—as important in castles to fending off conquers as forgetting Gilded Age woes. And for millionaire shoe baron Thomas Plant, that meant setting his 1914 Lucknow Estate (named after the Indian city he loved) on the rim of an extinct caldera high in the Ossipee Mountains with unbroken views over 6,300 private acres of woods and lakes.

Grey Towers Castle - Most colleges contend to be fortresses of learning, but Arcadia University in the suburbs north of Philadelphia can back it up with battlements acquired in 1929. Grey Towers was built by eclectic sugar refiner William Welsh Harrison between 1893 and 1898 and modeled after Northumberland's Alnwick Castle (a.k.a. the most archetypal expression of the medieval style).

'Iolani Palace - Other properties on this list may be bigger and more lavish, but the 'Iolani Palace has one thing above them all: legitimacy. America's only true palace—as in, royalty resided here—was built from 1879 to 1882 by King Kalakua and Queen Kapi'olani.

'Iolani Palace - Other properties on this list may be bigger and more lavish, but the 'Iolani Palace has one thing above them all: legitimacy. America's only true palace—as in, royalty resided here—was built from 1879 to 1882 by King Kalakua and Queen Kapi'olani.

Fonthill Castle - Celebrating its centennial in 2012, the former home of industrialist-turned-archaeologist Henry Mercer is an ode to artisanship: All 44 rooms (10 bathrooms, five bedrooms, and 200 windows), 32 stairwells, 18 fireplaces, and 21 chimneys are hewn from hand-mixed reinforced concrete in a mishmash of medieval, Gothic, and Byzantine styles.

Gillette Castle - It's elementary: Get famous (and rich) by playing Sherlock Holmes on the stage; build your own Baskerville Hall. Pet project of campy eccentric William Hooker Gillette, the 24-room castle was completed in 1919 by a crew of 20 men over five years using the actor/playwright's own drafts and designs. It's also the focal point of his 184-acre Seventh Sister estate, a forested bluff overlooking the Connecticut River.

OHEKA Castle - Second behind Asheville's Biltmore as the largest private estate in the nation, OHEKA—an acronym of Otto Herman Kahn, its millionaire financier original owner—ended up abandoned in the late 1970s and sustained extensive damage from fires, vandals, and neglect. After a 20-year renovation, it's back in form and is now a 32-room luxury hotel.

10 awe-inspiring American castles