Better than castles, there's privacy.
So much privacy that the airport shuts down at night. And the whole Caribbean island (part of the nation of St. Vincent and the Grenadines) has only about 17—17—public hotel rooms. And all the rental villas sit way low, below the treeline, confounding any paparazzi who might be lucky enough to wash up on the island's white sands.
Need more details on one of the most secluded vacations south of St. Vincent? No problem.
"You can only get there via boat or tiny prop plane," celebrity travel consultant Lyndsey Green tells me. "It's not the kind of island you can just travel to as a paparazzo.
"There's nowhere for them to really stay. They would have to go incognito as a wealthy family renting a villa."
Here's more: There are only 74 private villas available for rent. And one of those villas is all yours—if you have, say, $20,000 per week to spend.
Oh, and the island tends to have a lot of Michelin-level chefs available for hire at those villas. If you like that kind of thing.
If not, some of the villas have private spas. One has its own golf course.
"It's all very top of the line--high thread count sheets, new appliances, some come with private butlers," Green tells me.
As far as getting there, well, it goes like this, according to publicist Arlene Winnick, who represents BeautifulPlaces, which, in turn, rents out villas on Mustique: "You fly into Barbados and they 'send the plane for you.' Of course, you can also park your yacht in the harbor and come aboard that way."
Or, if you're a princess, you may be talking about a private plane.
There's even a general vibe of exclusivity on Mustique that can be tough for mere mortals to penetrate.
"Once upon a time, visitors had to be known and pre-approved before arriving," dishes Travelzoo top expert Jaime Freedman.
These days, anyone rich enough is technically welcome, but Freedman says she's sure that, to some extent, the pre-approval process is still alive and well on the island.
You may wonder what the royal couple might do when they're there. We're talking your typical luxury island stuff--fishing, rainforest hikes, scuba, tennis.
"It's also a very calm island," Green says.
Now that last bit sounds good—especially if, say, you're expecting a baby in July?