What is the best unexplained mystery?

1. I've posted this before, but it's still one of my favorites: The hidden shafts in the Queen's Chamber of the great pyramid. Since the shafts are too small for a person to fit through, there have been two separate attempts to send in specialized robots. The first time they sent up a robot they reached a dead end and what appeared to be a sealed door, complete with metal handles. A decade later they came back with a new robot equipped with a drill, only to find that behind the door lay... another door. And no one knows what's behind it or why the original builders would go through all of the effort and expense of constructing these shafts and doors. Edit: [here] (http://www.guardians.net/hawass/articles/secret_doors_inside_the_great_pyramid.htm) is an (admittedly outdated) article with some good info and photos, despite Zahi Hawass being a biased shithead [here] (http://www.ancient-origins.net/opinion-guest-authors/unraveling-mystery-great-pyramid-air-shafts-006602?nopaging=1) is another article with more in depth history and descriptions, oddly one of the most sober and scholarly articles on ancient-origins.net (my favorite source for getting weird with speculation about ancient things) Edit again: everyone who thinks they’ve solved this clearly hasn’t taken a look at a single photo or diagram. The shafts are 21x21cm (8.2x8.2in) large. They are not, and never were, human sized.
   — SirTitsworthEsq


2. The encephalitis lethargica epidemic that struck between 1915-1926. No one knows why it happened, nor has there been a recurrence since the initial outbreak. From [Wikipedia](https://en.wikipedia.org/wiki/Encephalitis_lethargica): The disease attacks the brain, leaving some victims in a statue-like condition, speechless and motionless. Between 1915 and 1926, an epidemic of encephalitis lethargica spread around the world. Nearly five million people were affected, a third of whom died in the acute stages. Many of those who survived never returned to their pre-existing "aliveness". "They would be conscious and aware – yet not fully awake; they would sit motionless and speechless all day in their chairs, totally lacking energy, impetus, initiative, motive, appetite, affect or desire; they registered what went on about them without active attention, and with profound indifference. They neither conveyed nor felt the feeling of life; they were as insubstantial as ghosts, and as passive as zombies."
   — idunniu


3. So the Monarch Butterfly migrates to Mexico and back every year. During the year there are a full 4 generations of butterflies that live and die during the journey. Upon returning back from Mexico, the butterfly manages to find the same trees it's relative started out at despite never having been there.
   — Dizneymagic






4. The disappearance of Nicolas Barclay/Frederic Bourdin. In 1994, San Antonio, Texas, 13 year old Nicolas Barclay disappeared from his home. 3 years later, Barclay was found huddled next to a phone booth halfway across the world in Linares, Spain. Authorities picked him up and reunited him with his family. However, certain things didn’t add up. Barclay had very little memory of what happened to him, and couldn’t give police a real answer as to how he ended up in Spain. Plus, his English was terrible, and when he did speak English it was with a heavy accent. This doesn’t make sense for someone who spent the first 13 years of his life in the United States, but these discrepancies were explained away by the fact that Barclay was probably just coping with the emotional trauma of being kidnapped to a foreign country and kept away from his family for 3 years. One thing no one could explain though, was that when Nicolas returned to the United States, his eyes were a different color than when he originally disappeared. Barclay tried to resume a normal life, enrolling back into his old school, moving back in with his family, etc. About four months after reuniting with his family, a private investigator discovered that Nicolas Barclay actually wasn’t Barclay, but a con artist named Frederic Bourdin. Bourdin was wanted by Interpol because he had a habit of stealing the identity of missing youths. Bourdin was arrested, but this brought about even more disturbing questions about Nicolas’s disappearance. Apparently, Nicolas was a very unruly and problematic child. He was always getting into trouble at school, and there were several police reports from his family’s house about domestic disturbances and arguments that worsened in the months before he went missing. Nicolas’s mom moved her brother into their house (Nicolas’s uncle) shortly before he disappeared to help give Nicolas some structure. It is rumored that he couldn’t handle Nicolas and instead killed him. This would explain why the family was so willing to accept someone who wasn’t their son as their lost boy. If it was believed that Nicolas was alive, any murder investigation would come to a halt. Even more interesting? After Bourdin was arrested police began re-opening and investigating the case, Nicolas’s uncle promptly killed himself.
   — KissedByFire2194


5. FBI most wanted cases are always fun to look at. some of my favorites are... Jason Derek Brown, former mormon, partier, surfer, and chill type of guy. kills a security guard and runs off. Hasn't been seen since 2005 ish except for a sighting in 2009 Robert William Fisher, former marine, kills his family and blows up his house. Hasn't been seen since 2001. Last sign of him was his abandoned car and his dog Nobody knows if he's still out in the woods or is just a pile of bones at this point. Donald Eugene Webb had been on the list for 26 years. You'd think he'd be all over the place but he was really hidden by his wife and passed away in 1999 when his body was finally found in 2017. not a fbi most wanted case but John list managed to disappear after killing his family and created an entirely new identity and remarried before being caught after almost 18 years edit: check out all top 10: https://www.fbi.gov/wanted/topten also, another one is WILLIAM BRADFORD BISHOP, JR. accomplished and smart former US State Department Foreign Service worker kills his whole family in 1976 and goes on the run ever since. not spotted since '94. he's 81 now though
   — donillarytrumpton


6. In Australia, in 2011, someone broke into a TV station and spent four hours flushing $100,000 down the toilet. It is mindboggling. Why?
   — ElbisCochuelo






7. [The disappearance of Brandon Swanson](https://www.reddit.com/r/UnresolvedMysteries/comments/1r1fkp/disappearance_of_brandon_victor_swanson/). In 2008 a teenager in Minnesota was driving to a friend's party when he crashed into a ditch. He called his dad to come pick him up, but his dad was unable to find him, despite being a long-time resident of the area. Eventually Brandon started walking and described what he saw as a city up the road that he was heading to. Abruptly, Brandon cussed and his phone went silent. His car was later found abandoned in the ditch as he had described, but no city could have been in the area where he was walking. To this day he is still missing, with little evidence found since. * edit: For everyone discussing drug use, his friends that night said that he had had one beer before leaving, but did not exhibit any signs of inebriation and was by all accounts acting sober. His parents have also said that he did not excessively drink and had never taken drugs. He was 19 at the time.
   — User_Name_ASDF


8. I'd say the East Area Rapist/ Original Night Stalker's identity is one of the craziest mysteries to me. He committed 40-50 rapes, around a dozen murders, called a few of his victims and still nothing is known about the guy.
   — samuraimegas