Imagine being on the archaeological dig of a lifetime, searching for dinosaur bones or ancient Egyptian treasures, when you finally find something embedded in centuries-old rock or sealed in a tomb that you know hasn't been opened in thousands of years. But it's not a bone or a gem "“ it's"¦ a Game Boy? How in the world did that get there? That exact situation hasn't happened yet, but some similar incidents definitely have. They're called "Out-of-Place Artifacts," or OOPArt: things that don't appear to make sense in the context that they were found. Sometimes a perfectly logical explanation is to be had, sometimes the whole thing is a hoax or a misunderstanding, and in some cases, we still don't understand what happened. Here are some examples of each.

maine penny1. The Maine Penny. So an archaeologist finds a silver coin while digging in Maine. No big deal, right? It is when the archaeological site was an old Native American settlement and the coin is found to be a piece of Norse currency dating from 1065-1080 AD. Although more than 30,000 pieces were recovered from the site, they were all Native American save for the coin. There's no evidence that the Vikings ever had a settlement there, however, and no evidence that they even came that far south in the interest of trade. The only Norse settlement ever found in North America is in Newfoundland. The strongest theory thus far suggests that Native Americans acquired it through their trades and travels. There's no doubt that the coin itself is authentic, but how it ended up at the site is still in question "“ was it planted or did it really end up in Maine by honest means?

2. Acambaro figures. In 1944, thousands and thousands of little figurines resembling dinosaurs were dug up in Acambaro, Guanajuato, Mexico. The problem? As far as we know, people and dinosaurs didn't exist at the same time, so the existence of ancient carvings depicting such creatures when the people carving them didn't have any knowledge of them "“ it doesn't make any sense. Some people insist that no one person or people could have possibly carved 32,000 pieces by themselves; the carvings must be evidence that people and dinosaurs did simultaneously exist. Others say that the fact that all 32,000 pieces are intact or cleanly broken (but still grouped within the collection) shows in and of itself that the collection is a hoax "“ in reality, nothing that old with that many pieces is ever found in its entirety. One dating technique found that the pieces did, in fact, date back to 2500 BCE. But when that technique was later improved and then repeated, the result was different and found that the pieces were much newer.

runestone3. The Kensington Runestone. If the Vikings didn't make it as far as Maine, they definitely didn't make it as far as Minnesota"¦ at least, we don't think they did. But the Kensington Runestone says otherwise. The stone was found tangled in the roots of a tree by a farmer and is covered in runes. Roughly translated, one side says "8 Geats and 22 Norwegians on ?? acquisition expedition from Vinland far west. We had traps by 2 shelters one day's travel to the north from this stone. We were fishing one day. After we came home, found 10 men red with blood and dead. AVM (Ave Maria) Deliver from evils." Another side says, "(I) have 10 men at the inland sea to look after our ship 14 days travel from this wealth/property. Year [of our Lord] 1362." Not only does the stone not make sense historically, some people have noted how sharp and well-preserved the carvings are and question if it should be that way after hundreds of years of exposure to the elements. However, what appear to be authentic glacier marks (which are thousands of years older than the carvings supposedly are) are also quite sharp and easy to see on one side of the stone, suggesting that however the stone was lying must have kept it relatively untouched.

4. The Gympie Pyramid. This one has pretty much been figured out over the years, but I'll give you the back story anyway. In 1975, a pyramid-shaped earthen terrace was discovered in Queensland. It was thought to prove that the ancient Egyptians had mining operations in Australia "“ not only did the pyramid "prove" this, but so did a stone block with inscriptions on it that was dug up in the same general area. Although most scoffed at such an idea, a small number in the archaeological community supported the theory that an ancient civilization of some sort "“ be it Egyptian, Chinese or South American "“ had inhabited the area. Much research was done and the reason for the pyramid shape was revealed: in the 1880s, a farmer constructed the terrace and retaining wall to try to slow erosion. Pretty simple explanation, huh?

5. The Saqqara Bird. Speaking of Egypt, it has its own weird artifact. The Saqqara Bird was found in a tomb in Saqqara and has been dated to 200 BC. A carving of a bird doesn't seem like a big deal, right? It wouldn't be, but some have theorized that the shape of the bird is much different than other carvings that exist from the same time period "“ namely, it looks more like a modern-day aircraft than a bird. This would indicate, of course, that the Egyptians had much more advanced technology than we have ever imagined. You might notice that the bird lacks a tailplane, which would really indicate that it was similar to our airplanes, but the thought there is that it originally had one and it has been lost over the years. Replicas of the Saqqara Bird with a tailplane have been made, but the reports as to how it functioned vary. Some people swear that it glided beautifully just like an airplane, and others say that even with the addition of the tailplane, the Bird didn't glide well at all and was clearly never meant to do as much.

MYSTERY stone6. The Mystery Stone. Construction workers were digging near Lake Winnipesaukee (anyone else immediately think of What About Bob?) in 1892 when they found a strangely-shaped lump of clay. When the clay was cleaned off, what was underneath was an egg-shaped rock covered with carvings "“ a rock not native to New Hampshire by any means. The carvings include an ear of corn, a face, arrows, dots and a spiral. There's a hole that goes right through the middle of the stone, which is what has helped us realize that the stone may not be what it was originally thought to be (a peace treaty between two Native American tribes). When an analysis of the bore hole was conducted, it was determined that it had been made with modern day equipment. To this day, that's really all of the information we have on the Mystery Stone. If you think you can figure out the enigma, though, the stone is on display at the Museum of New Hampshire History in Concord.

7. The Baigong Pipes. A group of American scientists were on the hunt for dino fossils in China when they stumbled upon this series of of mysterious, pipe-like structures. They're situated in front of a pyramid-like formation which contained the mouths of three caves, which is there the pipes seem to come from. Although two of the cave mouths have collapsed, the third (and largest) contains two huge pipes "“ we're talking up to 16 inches in diameter. So far these specific pipes have gone largely unexplained, leaving the door open for theories about aliens and advanced prehistoric technology and all of that fun stuff, but clues can be found in a couple of similar structures elsewhere in the world. In Louisiana, cylinders a lot like the Baigong Pipes were found in the Florida parishes "“ they were determined to have been formed naturally when ironstone formed around the tap roots of pine trees. The trees are long gone, of course, but the "pipes" were so enduring that they stayed put

head8. The Tecaxic-Calixtlahuaca head. A broken piece of statue found in Mexico seems pretty plausible, until you look closer at the poor decapitated piece: it appears to be Roman. The hairstyle and the beard match up closely with the style of Roman statues during the second century A.D. or so. So how did it end up in grave goods (items buried with a body) from pre-Columbian times, when we thought that had only occurred once, and nowhere near Mexico (The one time was when the Vikings made it to Newfoundland)? That's a good question, and one that is still in the process of being answered. Of course a lot of scientists and archaeologists are quick to point the hoax finger, but others argue that a shipwreck washed ashore could have eventually brought such an artifact to Central Mexico.

Do you know of any more artifacts that seem to be out of place? Those suspicious runestones seem to be scattered across the country "“ there's one in Oklahoma and one in Tennessee as well.