The biggest hole is in Milney, east Siberia, Russia. The average temperature in winter in Milney, a county which is only lower than the Arctic Circle, is about -40 Degree Centigrate.
The county was built in 1955. The geologists came to Tiolpxe area because of the abundance reserve of mineral. So, it fetures as hole of 11/2 miles wide and 500 metres deep, which now is a diamond mine.
There is the biggest adamas mine here in the world and 84.1% of the adamas resources are right here. There are 0.4g/ton in the primary ore. It was firstly found in 1949 and has been extracted widely since 1970's, which is almost as large as half of a city and now it has already been closed.