Darvaza Gas Crater, Turkmenistan, In 1971, geologists discovered a massive underground deposit of natural gas on this site. Whilst excavating the hole to tap the gas, the drilling rig collapsed leaving a massive hole. To prevent poisonous gasses from escaping, the hole was allowed to burn. It continues to burn to this day and has done so without ceasing
The Kimberley Diamond Mine (also known as the Big Hole) holds the (disputed) title of being the largest hand-dug hole in the world. From 1866 to 1914 50,000 miners dug the hole with picks and shovels, yielding 2,722 kg of diamonds. Attempts are being made to have it registered as a world heritage site.
Monticello Dam is a dam in Napa County, California, United States most noted for its large circular spillway with a rate of 48,400 cubic persecond
The Mirny Diamond Mine is 525m deep and has a diameter of 1200m. It was the first, and one of the largest, diamond Pipes in the USSR. It is now abandoned. While it was still operational, it would take two hours for trucks to drive from the top to the bottom of the mine.
Sink hole, Guatemala