Free

2.  Part of the Lighthouse Reef System, The Great
Blue Hole lies approximately 60 miles off the
mainland out of Belize City. A large, almost
perfectly circular hole approximately one
quarter of a mile (0.4 km) across, it’s one of
the most astounding dive sites to be found
anywhere on earth. Inside this hole, the water
is 480 feet (145 m) deep and it is the depth of
water which gives the deep blue color that
causes such structures throughout the world
to be known as "blue holes."

5.  This spectacular landform in Mauritania in the
southwestern part of the Sahara desert is so
huge with a diameter of 30 miles that it is
visible from space. Called Richat Structure --
or the Eye of the Sahara– the formation was
originally thought to be caused by a
meteorite impact but now geologists believe
it is a product of uplift and erosion. The
cause of its circular shape is still a mystery.

7.  Mato Grosso do Sul region in Brazil (and
especially the quiet town of Bonito) boasts many
marvelous underground lakes: Gruta do Lago
Azul, Gruta do Mimoso, Aquário Natural. The
world famous "Gruta do Lago Azul” (Blue Lake
Cave) is a natural monument whose interior is
formed by stalactites, stalagmites and a huge
and wonderful blue lake. The beauty of the lake
is something impressive. The Blue Lake Cave has
a big variety of geologicalformation but
impresses mainly for the deep blue colored water
of its inside lake.

11.  An area of about 40,000 interlocking basalt
columns, the Giants Causeway is a result of an
ancient volcanic eruption. Located on the north-
east coast of Northern Ireland, most of its
columns are hexagonal, although there are also
some with four, five, seven and eight sides. The
tallest are about 12 meters (36 ft) high, and the
solidified lava in the cliffs is 28 meters thick in
places. In a 2005 poll of Radio Times readers, the
causeway was named as the fourth greatest
natural wonder in the United Kingdom.

16.  Called by locals The Door to Hell, this place in
Uzbekistan is situated near the small town of
Darvaz. When geologists were drilling for gas, 35
years ago, they suddenly found an underground
cavern that was so big, all the drilling site with all
the equipment and camps got deep deep under
the ground. None dared to go down there
because the cavern was filled with gas, so they
ignited it so that no poisonous gas could come
out of the hole, and since then, it has been
burning. Nobody knows how many tons of
excellent gas has been burned for all those years
but it just seems to be infinite.

18.  The Wave Rock is a natural rock formation located in
western Australia. It derives its name from the fact that
it is shaped like a tall breaking ocean wave. The total
outcrop covers several hectares; the "wave" part of the
rock is about 15 meters high and approximately 110
meters long. One aspect of Wave Rock rarely shown on
photographs is the retaining wall about halfway up the
rock. This follows the contours and allows rainwater to
be collected in a dam. It was constructed in 1951 by
the Public Works Department, and such walls are
common on many similar rocks in the wheatbelt.

20.  Composed of around 1,268 perfectly cone-shaped
hills of about the same size spread over an area of
more than 50 square kilometres (20 sq mi), this
highly unusual geologicalformation , called
Chocolate Hills, is located in Bohol, Philippines.
There are a number of hypotheses regarding the
formation of the hills. These include simple
limestone weathering, sub-oceanic volcanism, the
uplift of the seafloor and a more recent theory
which maintains that as an ancient active volcano
self-destructed, it spewed huge blocks of stone
which were then covered with limestone and later
thrust forth from the ocean bed.