1. The Bronze Age Collapse and the Sea People

  The Bronze Age Collapse was a relatively sudden, likely violent, destruction of almost every advanced civilization around the Eastern Mediterranean around 1200 BC. The great Mycenaean civilization fell, as did their trade routes, and the collapse of trade likely hastened the fall of other powers that probably relied extensively on it.

  A mysterious “Sea People” are the main culprit. Egyptian records, some of the only that exist about the events, depict a “league” of nations that attacked them, and their neighbors, around the time of the Bronze Age collapse. These invaders, or groups of invaders not acting in accordance with one another, are believed to have overran almost every nation in the region. Before the chaos was over, cities across the Eastern Mediterranean were either in ruins, or were abandoned.

  Where they came from, and why, is still debated. There could have been an environmental change, or some agricultural problem, that pushed these people from their homelands, and hastened their plans for conquest. An earthquake could have disrupted trade to such an extent that it would have left dependent nations with few choices. The whole picture will likely remain unknown.

2. The Voynich Manuscript

  The Voynich Manuscript  is a codex written entirely in an unknown language. Carbon dating has established that it was written in the early 15th century CE. Given the illustrations, it is widely assumed to have been a pharmacopoeia.

  Here is a great article from the New Yorker: The Unsolvable Mysteries of the Voynich Manuscript

3. The Lost Colony of Roanoke

  The Roanoke colony was meant to be a permanent English settlement on an island off the coast of North Carolina. Established to bring the riches of the New World back to England, the colony was found to be deserted in 1586 by a charter seeking to establish another colony. Instead, they reestablished the Roanoke colony.

  John White, one of the leading colonists who resettled the colony, returned to England to ask for help. White’s return to the colony was delayed by the Anglo-Spanish war. When he finally did return in 1590, the colonists that were left behind had disappeared again.

  Numerous theories exist as to what happened to the colonists. It is believed that whatever befell them, some of the colonists likely could have survived, and ended up prisoners of, or coexisted with, American Indian tribes.

4. The existence of Atlantis

Very few experts still believe that Atlantis, as described by Plato in the 3rd century BC, could have existed. Plato states that Atlantis existed about 9,000 years before his time, and that the tradition he wrote about had been handed down orally over the generations.

  The story still gets interest today owing to the fact that it’s theoretically possible for an advanced seafaring civilization could have disappeared, or it could have been a reference to the Minoan Civilization. While the story appears to be pure mythology, Plato’s iconic legacy has also fueled outlying speculation.

5. The Mayan Civilization

  The Mayan civilization flourished in what has been deemed one of the cradles of civilization- the Mesoamerican region. They developed over thousands of years, and developed into an advanced civilization spread out across towns and city-states. 

  Like the Bronze Age Collapse, the disappearance of the Maya was likely brought about by a series of problems, such as depleted resources, conflict and changing environmental factors.