Among the amazing natural phenomena should be certainly included periodically widened holes in the earth on different locations around the world.
The biggest examples are introduced below.
. The first one is obviously - Kimberlitovaya Tube "Peace" (Mir diamond pipe), Yakutia.
The world's largest diamond mining quarry is amazing.
Another similar phenomena is Kimberlite pipe "Big Hole", South Africa.
At the site of the mine before (about 70 - 130 million years ago) was Vulcan .Amost hundred years ago - in 1914, developments in the "Big Hole" have been discontinued, but the gaping mouth of the tube remains to this day and now serves as tourist attraction , playing the role of the museum. And ... begins to create problems. There is a serious danger of crush not only of its edges but of roads nearby.