Some 250 million years ago, a part of Ukraine was under a shallow ocean. When the ocean dried up, it left behind a huge deposit of salt.
The Wieliczka Salt Mine located in the town of Wieliczka in southern Poland, lies within the Kraków metropolitan area.
The Naica Mine of the Mexican state of Chihuahua, is a working mine that is best known for its extraordinary selenite crystals.
The Mir mine, also called the Mirny mine, is an open pit diamond mine located in Mirny, Sakha Republic, in the Siberian region of eastern Russia. The mine is >525 meters (1,722 ft) deep (4th in the world) and has a diameter of 1,200 m (3,900 ft), and is one of the largest excavated holes in the world.
In 1959 it was the centre of project Military Atomic Energy Authority operation orpheus investigating the possibility of masking the seismic signal given out by underground nuclear tests.
Bagger 288 (Excavator 288), built by the German company Krupp for the energy and mining firm Rheinbraun, is a bucket-wheel excavator or mobile strip mining machine.