When a construction project kicks off, it’s exciting for everyone involved. Whether it’s a simple home renovation or a massive undertaking involving large crews, knowing the final product is going to look amazing has everyone ready to put in the legwork to get it done.

As thrilling as it can be to picture the end result, sometimes the most exciting things actually happen during the construction itself. Believe it or not, plenty of amazing—and valuable—items have been found right in the middle of a demolition project. Check out these 20 discoveries!

1. Mummified toddler: The apartment of a Parisian couple was being renovated when workers came across something startling: inside one of the walls was the body of a mummified toddler! No one was able to figure out who the child was or how his remains got there.

2. Gold and silver walls: A couple named Guiseppe Cadili and Valeria Giarusso purchased an apartment in Palermo, Italy, and they wanted to knock down some walls to make a larger room. That’s when they noticed a section of the wall was wet. After scrubbing down the room, they found ornate gold and silver paint covering each wall! Researchers said the apartment most likely belonged to a North African merchant in the 1700s.

3. Mayan drawings: The Ramirez family of Guatemala decided to do some kitchen renovations, and when they began stripping away the paint on the walls, they discovered ancient Mayan drawings depicting Spanish and Mayan people. Based on the number of drawings and intricate detail, archaeologists assumed someone important must have once lived there.

4. Victorian kitchen: One couple from Wales discovered an entire untouched Victorian kitchen in their basement that was sealed off after World War II. It was complete with perfectly preserved utensils, cookware, and even cookbooks!

5. Shipwreck: At a large construction site in Boston’s Seaport District, workers made an absolutely astonishing discovery. They found an entire shipwreck that dated back to the mid- to late-nineteenth century!

6. Letter to Santa: During World War II, a little boy named David wrote a letter to Santa Claus and hid it inside the chimney of his home. Seventy-two years later, a contractor named Lewis Shaw found the letter while demolishing the home. Amazingly, through social media, Lewis tracked down David and returned his letter!

7. Mummified woman: In 2011, in the city of Taizhou, China, a 700-year-old mummy was found by construction workers beneath a road. The mummified woman was apparently a member of the Ming Dynasty; she was dressed in silk clothing and wore expensive jewelry.

8. Mansion foundation: In 2013, during the construction of a housing development in Wellington, England, excavators came across the foundation of a mansion dating back to the 12th century! Oddly, archaeologists couldn’t find any historical records of its existence.

9. African burial ground: In 1991, during the development of a new building in lower Manhattan, New York, workers uncovered a 17th-century African burial ground. The site was soon recognized as a national landmark, and in 2006, then-president George W. Bush declared the site as such.

10. Woolly mammoth tusk: During the construction of a residential building in Seattle, Washington, the fossilized eight-foot tusk of a woolly mammoth believed to be 60,000 years old was found beneath the foundation’s frame! It was soon taken to Seattle’s Burke Museum of Natural History and Culture.

11. Time capsule: A 121-year-old time capsule was once discovered underneath a bridge in the Cairngorms National Park in Scotland. Some of the items included were a bottle of whisky, a newspaper from 1894, and a scroll.

12. Hospital: In 2013, a construction crew in Madrid, Spain, began building a new Apple store when they came across something surprising: the foundation of a hospital. But it wasn’t just any hospital; this one helped people who contracted the bubonic plague during the 15th century!

13. Coffins: In 2017, during the construction of an apartment complex in Philadelphia, Pennsylvania, crews found two dozen coffins in near-perfect condition—with intact humans remains inside. It was speculated they were from an 18th-century burial ground for the First Baptist Church.

14. Byzantine church: Along the side of a road in Israel, just outside of Jerusalem, construction workers who were performing routine maintenance uncovered the remnants of a 1,500-year-old Byzantine church!

15. Bomb: A total of 3.4 million tons of explosives were dropped on various countries during World War II, and it’s possible as many as 15 percent of them didn’t detonate. In 2016, on Christmas, a 4,000-pound bomb was discovered underneath a construction site in Augsburg, Bavaria.

16. Superman comic: A contractor named David Gonzalez purchased a 1938 home hoping to do some major renovation. As he was tearing down the walls, he realized the previous owner used newspapers as insulation—and hidden among the papers was an original Action Comics comic book featuring the debut of Superman. The comic sold for a whopping $175,000 at auction!

17. Cash: Sarina Jennings and Clinton McCallum of Arizona bought their first home and immediately began renovations. While tearing down a wall, their contractor found suitcases full of cash totaling $500,000! Unfortunately for the couple, a judge had the money returned to the original owner’s heirs.

18. Monopoly floor: A man named Nyeland Newel began renovating his California home and his first task was tearing up the carpet. After ripping up the carpet in his bedroom, he discovered a massive Monopoly game board painted on the hardwood floor!

19. Maps: When the Watkins family of Yarmouth, Nova Scotia, started some home renovations, they, too, began by ripping up the carpets. The insulation underneath contained old newspapers and maps dating back to the 19th century!

20. Ancient Roman artifacts: Luke Irwin from Tisbury, England, was having some lighting installed in a barn in his backyard when workers came across several unusual artifacts buried nearby. As it turned out, Luke’s home had been constructed on top of a Roman villa, and the coins, animal bones, and artifacts they found were from 220 A.D.!