It's challenging to pinpoint truly "unknown" facts, as knowledge is continually evolving, and what may be unknown to one person might be well-known to another. However, I can share some lesser-known or less widely discussed facts about the world:

 Bananas are berries, but strawberries aren't: 

In botanical terms, bananas qualify as berries because they develop from a flower with a single ovary. On the other hand, strawberries are not true berries because they come from a flower with multiple ovaries. 

 The shortest war in history: 

The Anglo-Zanzibar War, fought between the United Kingdom and the Sultanate of Zanzibar on August 27, 1896, lasted only 38 minutes. 

  Honey never spoils:

Archaeologists have found pots of honey in ancient Egyptian tombs that are over 3,000 years old and still perfectly edible. Honey's natural composition makes it an inhospitable environment for bacteria and microorganisms. 

  Antibiotic resistance in soil bacteria:

Long before humans started using antibiotics, soil bacteria were producing similar substances. The genes responsible for antibiotic resistance have been found in ancient permafrost soil samples, suggesting that antibiotic resistance is a natural phenomenon. 

  The Great Emu War:

In 1932, Australia declared war on emus. Farmers were dealing with a large population of emus causing agricultural damage. The government sent soldiers armed with machine guns to combat the emu population, but the operation was ultimately unsuccessful. 

  Lake Baikal is the world's deepest freshwater lake:

Located in Siberia, Russia, Lake Baikal is not only the deepest but also the oldest and clearest freshwater lake on Earth. It reaches a depth of about 5,387 feet (1,642 meters). 

  The world's quietest room:

The anechoic chamber at Orfield Laboratories in Minnesota holds the Guinness World Record for being the quietest place on Earth. The absence of sound is so extreme that people can hear their own blood circulation and the sound of their joints moving.

 

  The Baltic Sea Anomaly:

A mysterious object lying at the bottom of the Baltic Sea, discovered in 2011, has been the subject of much speculation. Some believe it's a natural formation, while others suggest it could be a sunken UFO.

 Remember, the definition of "unknown" can vary from person to person, and some of these facts might be more familiar to certain individuals or communities.