One of the most infamous killers of all time, Jack the Ripper terrorized women in late 1880s London. Despite taunting police with letters, his (or her) identity was never found. Many people have theories, but there is no concrete proof.

In 587 B.C. the Babylonians conquered Jerusalem, destroying the First Temple in the process. In that temple sat the Ark of the Covenant, and the ten commandment tablets. Nobody knows if the Ark was hidden, destroyed, or even carried back to Babylon. At this point, we’ll probably never know.

The iconic British landmark likely began construction around 3100 BC, with more portions added as time went on. Whatever culture built the monument left no written records, but obviously understood concepts such as the summer and winter solstices. As one of the world’s oldest landmarks, it’s unlikely we’ll be discovering anything new about it.

Portrait of a Young Man by Raphael went missing at the end of WWII, and has yet to be found again. All signs point to it having been sold for traveling money by German Hans Frank.

The tombs of Alexander the Great, Cleopatra and Marc Antony have never been found. They are all most likely buried beneath the modern city of Alexandria, but good luck digging for them.

Contrary to popular belief, Jesus was not born on December 25th. Instead, that date was likely chosen as a way to merge the holiday with other Roman rituals, and facilitate conversion to Christianity. Ultimately, his real birthday remains unknown, and even the exact year is up for debate.

In 1587, John White arrived at Roanoke Island with 120 people, before returning to England for more supplies. When he came back, every single new colonist was missing, and only the word “CROATOAN” carved into wood gave any clue as to what happened. To this day, nobody knows exactly what happened to those colonists.

The Teamster union leader and criminal was killed in 1975. Despite an extensive investigation by the FBI, neither his killers nor his body were ever found. A more recent tip towards a New Jersey landfill produced no results. Rumors that he was buried under Metlife stadium are also false.

Although we can reasonably assume that Amelia Earhart crashed into the Pacific Ocean during her attempt to become the first woman to fly around the world, the exact location of the wreckage was never found. The failure of extensive search and rescue operations have led many to form their own conspiracy theories.

We will probably never know what lies within the First Qin Emperor of China’s tomb. The Qinshihuang Mausoleum exists, and we know exactly where it is, but the only part of the site that's been extensively excavated for artifacts is the famous Terracotta Army. The main tomb itself is still completely sealed, and no attempts have been made to open it. Legends state that it is not just full of treasure, but extensively boobytrapped. At this point, it’s too risky to even try and get in.

In 1963, President John F. Kennedy was shot and killed by Lee Harvey Oswald in Dallas. However, before Oswald could stand trial, he was shot and killed by a man named Jack Ruby. Nobody knows for sure whether the murders were related, but it seems plausible that Oswald was silenced from revealing a bigger scheme. Ruby died a few years later, so we’ll probably never know.

In 2014, a Malaysian Airlines flight was lost over the South China sea, and was never found. It is the most perplexing and deadly case of a missing aircraft in aviation history. Very little evidence has been found, despite the assistance of modern technology.