3.  Racetrack Playa is a dry lake found within Death Valley
National Park, California, U.S.A.
 Racetrack Playa is a magnificent place to visit, because
of a very mysterious geological phenomenon that takes
place here.
 The Racetrack Playa is where stones move by
themselves with no animal or human intervention.
 The mystery of the Death Valley moving stones is far
from being resolved.

5.  Estimates say that Crop circles appear every week
somewhere around the world.
 The strange circles and patterns appear mysteriously
overnight in farmers' fields, provoking puzzlement,
delight, and intrigue for both locals and the news
media.
 The circles are mostly found in the United Kingdom,
but have spread to dozens of countries around the
world in past decades.
 This mystery of crop circles is still being discussed and
is not solved.

7.  Hessdalen Light is an unexplained light phenomenon
that occurs in Hessdalen valley of Norway.
 They were observed over 15 to 20 times per week from
1982 until 1984, since then, the activity has decreased
and now the lights are observed about 10 to 20 times
per year.
 The Hessdalen light most often is a bright, white or
yellow light of unknown origin floating above ground
level lasting sometimes for more than an hour.

9.  For decades, the Atlantic Ocean’s fabled Bermuda
Triangle has captured the human imagination with
unexplained disappearances of ships, planes, and
people.
 Some speculate that unknown and mysterious forces
account for the unexplained disappearances, such as
extraterrestrials capturing humans for study.
 The ocean has always been a mysterious place to
humans, and when foul weather or poor navigation is
involved, it can be a very deadly place.