It's the Kola Superdeep Borehole, in Russia. Drilling began in 1970 and reached a depth of 7.5 miles. The distance from the Earth's surface to its centre is around 4000 miles.

Since 2008 the remote drilling site has lain abandoned and the hole welded shut. Broken down equipment and derelict buildings litter the site. This is a photo of the welded-up hole: http://photos.wikimapia.org/p/00/04/37/55/36_big.jpg