Some inexplicable phenomenon

 Yeti

The Yeti or Abominable Snowman is an ape-like cryptid said to inhabit the Himalayan region of Nepal, India and Tibet. Many people saw him but no one knows who he is.

 Ghosts

People saw ghost in ancient times and they still see them nowadays. Maybe they really exist, but we can’t say for sure.

 Déjà vu

It may be translated from French like “Already seen before”. It is not uncommon when a place a person has never been to looks familiar to him.

 Taos noise

Inhabitants and tourists of Taos city hear strange light noise coming from the desert. But the source of the noise has not yet been discovered.

  UFO

Unknown flying objects do exist for sure. But still this phenomenon is inder the veil of secrecy.