Built as the Vienna home of Philip of Württemberg, the Hotel Imperial originally housed the prince from 1863 to 1865, until a city planning problem saw him move on.
In 1873, an investor bought the property in time for that year's Vienna Expo, converting the numerous halls into individual hotels rooms while retaining many regal touches.
Little has changed since, with the palace's 150-year history available to all who stay at the hotel: ornate 19th-century chandeliers, crest-embossed drapes and endless relics.
Highlight: The traditional personal butler service, which comes with every suite.
Hotel Imperial, Kärntner Ring 16, 1015 Vienna, Austria; +43 1 50 1100
Hotel Gritti Palace, Venice, Italy
Venice has an endless number of "palaces" converted into hotels, but few match up to the opulence of the Gritti.
Constructed in the 16th century for the city's "Doge" (Duke), it was later used to welcome Vatican ambassadors, before finally being turned into a hotel in the late 1800s.
Following a 15-month renovation, the hotel reopened this spring, with each of its 82 rooms restored with the Renaissance in mind.
Highlight: The Explorer's Library, paying homage to the hotel's many literary guests, including Ernest Hemingway and W. Somerset Maugham.
Hotel Gritti Palace, Campo Santa Maria del Giglio, 2467 30124 Venice, Italy; +39 041 296 1222
Chateau de Saint-Loup, Loire Valley, France
The year is 1356 and the Hundred Years' War ravages on -- the Battle of Poitiers has just taken place and Edward the Black Prince has captured the King of France, Jean le Bon, imprisoning him in a castle keep in the Loire Valley.
Jump forward nearly 700 years and that keep still stands as part of the privately owned Chateau de Saint-Loup hotel.
Guests are treated to a truly medieval experience, with accommodation choices in the gorgeous 17th-century chateau, in the 12th-century tower square or within the keep itself.
Highlight: The appropriately named Black Prince suite, with such medieval touches as his-and-her baths and a granite fireplace.
Chateau de Saint-Loup, 79600 Saint-Loup-Lamairé France; +33 5 49 64 81 73
Amberley Castle, Sussex, England
Dating back more than 900 years, Amberley Castle was once owned by Queen Elizabeth I. Today, the castle incorporates 19 spacious yet traditional suites, a tennis court and a golf course.
Battlement towers previously used to keep watch on the numerous conflicts in the area still keep watch, and an 18-meter high wall still stands.
Highlight: The still-working portcullis, which is closed every night just past the stroke of midnight.
Amberley Castel, Amberley, Arundel, West Sussex BN18 9LT; +44 017 9883 1992
Ciragan Palace Kempinski, Istanbul
Considering Istanbul's strife-torn history, it's almost a miracle the Ciragan Palace has survived. It housed two separate sultans during its lifetime, before a great fire destroyed much of the site in the early 1900s.
In 1989, a Japanese company bought the site and restored its original architecture as a hotel complex. It's now run by the Kempinski Hotels group and a recent 2007 renovation has seen even more palatial features reinstated.