Kola Superdeep Borehole
The greatest depth was reached in 1989. The people making the hole thought that they would get to  by the end of 1990 and, at last, get to 15,000 m by 1993. They were not able to go any deeper, though, because they had made an error, and the end of the hole was  in place of the  they had hoped for. Their machines stopped making any holes at all in 1992. The last studies were stopped in 2005 and the place was completely closed and left alone in 2008.