1. Ilha da Queimada Grande
Ilha da Queimada Grande, or “Snake Island,” is an island off the coast of Brazil that’s home to a rare and incredibly deadly species of snake called the golden lancehead. According to some estimates, there are one to five snakes for every square meter of land on the 43-hectare island. (A population survey of the area indicated that those numbers are probably an exaggeration, but even so, there are definitely a lot of snakes on the island.)
The vipers mainly eat the migratory birds that visit the island, and they’ve evolved a venomous bite strong enough to take down their prey before they can fly away. The snakes are so dangerous that the Brazilian government has forbidden people from visiting the area. Rare exceptions are made, mostly for scientists studying the species, but they have to be accompanied by a doctor—just in case.
2. Lascaux Cave
Though not many people are eager to go to Snake Island, you may be sad to hear that you can’t visit Lascaux Cave in France. Discovered in 1940, the cavern contains some of the most iconic cave paintings ever studied. The sketches of horses, deer, and other animals date back to the Upper Paleolithic period, 15,000 to 17,000 years ago. The cave opened to the public in 1948 and closed permanently after just 15 years. The artificial lights installed there had been promoting algae growth on the cave walls and causing the painting’s colors to fade. (The microbes humans brought in with them apparently weren’t helping, either.) Lascaux Cave is now off-limits to visitors, but archaeology fans can check out a perfect replica of the site located right next door.
3. Ise Grand Shrine
The first iteration of this Shinto shrine in Japan was constructed around 2000 years ago, and since the late 7th century, it’s been torn down and rebuilt every two decades. This tradition symbolizes the Shinto concepts of death and rebirth, but it has practical purposes as well. Reconstructing the shrine about once a generation helps keep the traditional shinmei-zukuri architectural style alive. Wood also has a shorter lifespan than most building materials, so demolishing the shrine before it can rot is a way to beat nature at its own game.
When Ise Grand is rebuilt, every detail of the ornate design has to be replicated, making it one of the most expensive structures in the country. Reconstructing Ise Grand and its hundreds of secondary shrines costs the Japanese government $500 million each time, and most of that cost and effort ends up going unseen: While tourists can view it from the outside, the inside of the shrine is only accessible to the highest priestesses or priests.
4. The Svalbard Global Seed Vault
The Svalbard Global Seed Vault is located on the remote Arctic island of Spitsbergen in Norway. The 11,000-square-foot space houses more than 1 million seed samples native to places around the world. The vault acts as a sort of back-up drive of the world’s crops, preserving specimens in a safe place in case a disaster ever wipes them out in their natural environment. The facility is built to protect its contents from unwanted visitors along with everything else. It’s deep enough underground and high enough above sea level to withstand earthquakes, ocean rise, and nuclear attacks.
5. The Vatican’s Secret Archives
Millions of people visit the Vatican in Rome each year, but there’s at least one area in the tiny sovereign state that’s strictly off-limits. Established in 1612, the Vatican Apostolic Archive (formerly the Vatican’s Secret Archives) contains the personal documents of all the popes. The archives were completely classified until 1881, when Pope Leo XIII gave Catholic scholars special access to the materials. Today, the collection remains closed to everyone but certain accredited scholars. Researchers who are allowed inside can request up to five files a day, but they have to know exactly what they want because browsing is forbidden. Who knows what we’d find out if they let Tom Hanks run loose in there for a few hours.