Inside Mustique, Prince William and Kate Middleton's celeb-favorite Caribbean vacation spot

The Duke and Duchess of Cambridge are vacationing on a private Caribbean island, but thanks to social media, we're able to take a peek inside.

This is Prince William and Kate Middleton's latest of many visits to Mustique, which is located within a chain of islands in the West Indies. It's been a favorite spot of royals for decades: Princess Margaret was one of the first people to begin frequenting the beautiful, then minimally-developed spot in the early 1960s. As it began to flourish as a destination for the extremely wealthy, Queen Elizabeth II and the Duke of Edinburgh were known to visit in the mid-20th century.

"There are no rules on Mustique, no protocols or expectations," the island's official website reads. "Guests can simply do as they wish."

PHOTOS: Inside the ultra-private island of Mustique

The island's no-fly policy is a big privacy feature for not only the royals, but also a handful of major celebrities who've vacationed in Mustique over the years. Paul McCartney, Jon Bon Jovi, Denzel Washington, David Bowie and Mick Jagger are among those names.

Even though the island is incredibly expensive and boasts remarkable privacy, its social media team does share enviable photos to Instagram. The snapshots don't, of course, feature the recognizable faces who like to visit. A tight security list ensures that nobody unapproved makes it onto the land.

While the Duke and Duchess are visiting on holiday, there is some minor royal work element to the trip: Prince William is technically second-in-line to its throne.

You can read more history of the island, and see vintage photos, here on Mustique's official website.

PHOTOS: Kate, Will and their three children in 2019