The aerial school landings in Zimbabwe. 60+ school children saw crafts landing and beings coming out of them. The kids interacted with the beings. They were put under evaluation by a Harvard psychiatrist. They all told virtually the same story and drew the same drawings. It was concluded that they were telling the truth.-u/Equivalent-Quail3995

The identity of the Zodiac Killer hands down. It hasn't been solved despite what you read about Gary Post.-u/1man2barrels

The disappearance of the Springfield Three is a top contender for me.Long story short, in the early morning hours of June 7, 1992, these three women, Sherrill Levitt (47), her daughter Suzanne 'Suzie' Streeter (19), and Suzie's friend Stacy McCall (18) all vanished from Sherrill and Suzie's home following a night of fun and partying as it was the girl's high school graduation.

All their personal belongings, their cars, purses, and even the little dog was left behind. There were no signs of a struggle or foul play, however, the front porch light's glass globe was broken and not swept up, and there was a weird message on the answering machine that accidentally got deleted. Yet, no trace of the three women has ever been found and the case remains unsolved 30 years later.-u/Bjnboy

My favorite is the Chicago TV hijacking. During a 'Dr. Who' rerun in 1987 somebody dressed as Max Headroom hijacked the tv signal for a minute and a half during which he exposed his a** and got spanked by a woman and mocked coca-cola. FCC has been investigating for years and nobody has been charged.-u/KhaosKake

One I’m always fascinated with is I believe in the mid-2000’s a student at Ohio State mysteriously disappeared and to this day, they have no idea what happened to him. Basically, he went out to a popular bar with friends, the security camera sees him walking into the bar and this is the only entrance/exit as the bar is in a larger building but it never sees him leave the bar at the end of the night. His name was Brian Shaffer. It’s an interesting story/mystery to take a look at.-u/TrainingRegistration

What happened to the 3 escapees of the "inescapable" Alcatraz? Whether they did survive or not, but if they did, that's one heck of a plan to escape undetected till to this day.-u/Leveolizan

The disappearance of Asha Degree. In 2000, 9-year-old girl that packed a bag in the middle of a storm and was last seen walking down a highway. A driver approached her to help and she ran into the woods and was never seen again.

Nothing suggests why she would run away. Her book bag was found a year later. Most likely she was abducted while walking but why did she leave her house in the middle of a “raging storm”?-u/palabear

Where is the tomb of Alexander the Great?-u/bdaydeedayday

The mystery of Kasper Hauser, a youth found wandering Germany in 1828 wearing undersized clothes and no communication skills. After being educated, he claimed to have grown up in the total isolation of a darkened cell. Years later he died after being stabbed by "a stranger" who gave Kasper a cryptic note, but officials suspected he stabbed himself.-u/Neon_Parrott

Where is Shelly Miscavige?-u/Bucketlist074

America's lost child AKA The boy in the box. He was discovered in Philadelphia, Pennsylvania on February 25th, 1953 having a fresh haircut, nail trims but had been severely beaten. Police ruled it off as a homicide and the case is still open to find the murderer.-u/OldmanHosea

The "Adam" case, where a little boy's torso was found in the River Thames. Investigators believe that he was trafficked from Nigeria to be murdered in a ritual sacrifice, but his body has never been formally identified.-u/whitewidow33B

Who really murdered the Princes in the Tower?-u/MRCHalifax

Collapse of the Bronze Age.-u/guitar_collector

The Wow! signal. A strong narrowband radio signal detected on August 15, 1977, by the Ohio State University's Big Ear radio telescope in the United States.-u/SuvenPan

The Vegas mass shooter who was a perfectly contented millionaire with a happy life and just opened fire on people from a hotel room…. What was that about? -u/fernincornwall

The Chicago Tylenol murders in 1982. Who would do such a thing and why? Was it one person acting alone? Did they do it at the distribution center, or did they go to different locations to tamper with the bottles?-u/kboody22

Who was Jack the Ripper?-u/Supraman83

The consciousness. A child is conceived, and at some point, once the brain becomes complex enough, it starts to develop a feeling of self. It starts to perceive itself as the center of something, and everything else is outside. We naturally distinguish the “I” from the rest of the world.

This is a light that goes on in the head at some point. In deep sleep, under narcotics or after injury, the light can flicker or go out. When we die, the thing that is me is gone forever. Or is it? Religion says it’s not. It’s an everyday mystery that gets more mysterious the more we think about it. I find this to be the most fascinating question there is.-u/Speedperson

My favorite is the Black Dahlia because the killer seems so obvious and yet it remains unsolved.-u/haesslichryn

What happened to the Sodder children?-u/i-love-cats-2020

Where that weird "S" that we all drew on our folders in high school actually came from?-u/DrKliever

D.B. Cooper. -u/MrRonObvious

The Hinterkaifeck murders. Whole story is absolutely horrific and they never discovered who actually committed the crime.-u/ConstantMelancholia

What information was burned in the Library of Alexandria?-u/LegitimateLobotomy