Earlier this month, four rooms of century-old chalkboard drawings were discovered during renovations at an Oklahoma City High School. The charming sketches of pilgrims, turkeys, and little girls blowing bubbles date to 1917, when they were covered up by a new layer of blackboards, and their unveiling provided a fascinating glimpse of what school was like at the beginning of the 20th century.

Finds like these inspire a sense of awe, but they’re not as rare as one might think. Over the past few years, the press has reported on a number of “time capsule” rooms—perfectly preserved spaces that exist in a state of suspended animation, usually (but not always) after being abandoned and forgotten. Some of these spots have been or will be turned into museums, but nothing will compare to being one of the first inside after decades of decay. These finds also raise a wonderful question: How many other treasure troves are sitting behind locked doors and bricked-up walls, just waiting to be discovered?

1. Maison Mantin // Moulins, France 

Louis Mantin was a relatively unremarkable French civil servant until his early 40s when he inherited a fortune from his father and reinvented himself as a gentleman of leisure. He devoted much of that fortune to constructing a mansion on the site of a former Bourbon palace in the town of Moulins, filling it with tapestries, paintings, and porcelain, and installing his personal collection of Egyptian antiquities and medieval locks, among other effects. (He even created a special pink-and-gold room for his mistress.) When he died childless in 1905, he left a will bequeathing his mansion to the town, and specifying that it should be turned into a museum 100 years later. Locals say it was his way of ensuring that he would never be forgotten. The house fell into a state of ruin until 2005, when it was finally reopened. Water, mold, and worms had heavily damaged the structure, but conservators mounted a full restoration to return things to their original opulence. Maison Mantin opened as a museum in 2010—only five years behind Mantin’s schedule. 

2. Edwin Booth’s Apartment // Player’s Club, NYC

Edwin Booth is best known as the older brother of John Wilkes Booth, Abraham Lincoln's assassin, but he was also one of the most celebrated actors of his day. In 1888, he opened a swanky gentlemen's club devoted to raising the position of actors in society. Mark Twain and William Tecumseh Sherman were co-founders, along with other local pillars of the arts and industry. The Gramercy Park townhouse also included Booth’s own living quarters, where he died, in his daughter's arms, in 1893. According to club lore, the room was locked up after Booth’s death and has been left virtually untouched ever since, apart from occasional dusting. The space apparently still smells like Booth’s tobacco smoke, and includes his furniture, velvet-lined makeup box, volumes of Shakespeare, and a human skull that, according to the club's website, "Booth saluted hundreds of times while playing Hamlet. The skull is said to be that of a horse thief who asked just before being hanged that his skull be given to Booth’s father, whom he admired."

3. Mrs. De Florian's apartment // Paris 

The experts who first stepped inside this Parisian flat in 2010 said it was like stumbling onto Sleeping Beauty's castle—untouched for decades and blanketed in a thick layer of dust. The apartment's former owner, one Mrs. De Florian, had left Paris amid the encroaching Nazi threat in the 1940s and never returned, eventually settling in the south of France. Seventy years later, she died at the age of 91, and her heirs hired professionals to inventory her belongings. It was only then that her apartment was finally re-opened, revealing faded but ornate furnishings and draperies, as well as a stuffed ostrich and a pre-war Mickey Mouse.

There was also a particularly special surprise: a painting of a lovely young woman in pink. It turned out to be the handiwork of one of Paris' most important Belle Epoque painters, Giovanni Boldini. And the woman in pink was Mrs. de Florian’s grandmother, Marthe de Florian, a Belle Epoque actress and socialite who had been Boldini's mistress. (The apartment also contained some of their love letters.) The art world swooned over the story, and the painting sold for $3 million at auction

4. Hubert Rochereau's bedroom // Bélâbre, France 

Lieutenant Hubert Guy Pierre Alphonse Rochereau died in 1918 at the age of 21, after being wounded during a World War I battle over a village in Belgium. His grief-stricken parents left his room more or less exactly as it was the day Rochereau left for the front—even going so far as to brick up the entrance. When they bequeathed the house to a friend in 1935, they stipulated that Hubert’s room shouldn't be changed for 500 years. The clause didn't have any legal backing, but it's been honored ever since, and the house is today owned by a retired local official who respects the request. Hubert’s room still includes his spurs, sword, helmet, and military jacket, as well as his pipes and books, and a lace bedspread covered with his war medals. 

5. Bellosguardo // Santa Barbara, Calif. 

Huguette Clark was the youngest child of copper baron, senator, and founder of Las Vegas William Andrews Clark. Shy and artistic, she had only a small circle of friends, and eventually spent the last 20 years of her life in a hospital room, even though she wasn’t sick. Meanwhile, her vast and secluded estate in Santa Barbara, known as Bellosguardo, was meticulously maintained for nearly 60 years at a cost of tens of thousands per month, even though no member of the family had visited since the 1950s. For decades, the only permanent resident of the 23-acre, French-style chateau was the estate manager, his dogs, and some foxes.

When Huguette inherited Bellosguardo in 1963, she reportedly told the staff that everything was to be kept in "first-class condition," and absolutely nothing should change. Linens were wrapped in brown paper in the 1960s, and dishes washed, covered, and dated in the 1990s. Staff worked tirelessly to keep things in perfect order—even though no one ever visited. Clark died in 2011 at the age of 104, and her (hotly contested) will stipulated that Bellosguardo estate be left to a new foundation to foster the arts.

Bellosguardo wasn’t her only property—she had a mansion in Connecticut that was never occupied, and three apartments on Manhattan’s Fifth Avenue, all filled with rare antiques, books, and art, which she never set foot in during her 20 years in the hospital. 

6. Play area in an Anglican Church // Liverpool 

For years, the reverend at the Anglican Church of Our Lady and St. Nicholas in Liverpool had heard rumors about an abandoned room up on the building’s upper floor. In 2014, he finally opened the trap door in the church's ceiling to discover a treasure trove of old toys, books, and snacks (including packages of vintage hot chocolate). Church officials believe the room was a play area sealed before the church was bombed during World War II, and then left sealed during reconstruction. Amazingly, one of the books dated back to 1696. 

7. World War I shelter // near Carspach, France 

In 2010, workers excavating for a road project in northern France discovered an elaborate underground shelter used in World War I. The tunnel had collapsed during heavy French shelling in 1918, killing all 34 German soldiers hiding out inside. Troops hauled out 13 of the bodies but considered it too dangerous to remove the rest, and the shelter sat abandoned until the 21st century. Archeologists who explored the shelter in 2011 found it had been built with room for 500 men, and came equipped with heating, telephone connections, electricity, and its own goat. They also found the remains of 21 soldiers inside, plus various personal effects—including wallets, glasses, dog tags, a wine bottle, a mustard jar, and a rosary made with a French bullet. 

8. Corner shop // Accrington, Lancashire

The council workers who paid a 2008 safety visit to a boarded-up shop in Lancashire might have been expecting to find some old newspapers and a rodent guest or two. Instead, they discovered the corner drugstore and ice cream parlor just as its last owners had left it more than 30 year earlier. (For reasons that are unclear, no one in the family-owned shop ever came to clear the place out.) And the erstwhile owners weren't great about rotating their stock: the workers found a repair bill from 1927, magazines from the '30s detailing the young Princess Elizabeth's travels, and ancient medicines including "Fennings Fever Mixture," "Victory V lozenges," and something called "Dulcet Cream." The safety check was carried out on behalf of a developer who planned to turn the shop into a house and gave some of the strange prizes inside to his workers. 

9. Pineheath House // Harrogate, Yorkshire

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The 40-room Pineheath House in Yorkshire was once owned by Indian-born aristocrats Sir Dhunjibhoy and Lady Bomanji, both active in early 20th century English and Indian high society. But after Lady Bomanji died in 1986, the property was occupied by their daughter, who changed nothing for 27 years. The developer who bought it in 2013 found it decorated in a 1920s style, and filled with products, newspaper clippings, and society invitations from throughout the 20th century. The mansion even had its own internal telephone system, used by the couple and their servants when they resided there each autumn. 

10. Scott’s Hut // Cape Evans, Ross Island, Antarctica 

In 1911, Captain Robert Falcon Scott and his men constructed a wooden hut on Ross Island in Antarctica to serve as their base of operations—one of the first human dwellings constructed on the continent. In January 1912, they set off for the South Pole, never to return. (Their frozen bodies were discovered later that year.) The hut—made of layers of wood prefabricated in England and insulated with shredded seaweed sewn into quilting—was used by a few more rounds of explorers, then sat untouched from 1917 until the 1950s, when a U.S. expedition dug it out of the snow and ice. Since then, it's been stabilized, repaired, and repainted, but much of the hut remains as the explorers left it, down to the bottles on the dining table and the reindeer-skin sleeping bags. Today, you can see the exterior and have a look around on Google Street View