The deepest hole people have ever made is on the Kola Peninsula, near Russia’s border with Norway. Soviet drillers began it in May 1970, and in 1989 one branch reached 12,262 metres: about a third of the way through the crust there, and roughly a fifth of one per cent of the way to the centre. The plan was 15,000. At the bottom the rock was about 180°C, hotter than anyone had forecast, and the layer of basalt the seismologists had promised at seven kilometres never turned up; it was granite all the way, changed by the pressure. Somewhere around six kilometres down, the cores brought up fossils of microscopic plankton. The money ran out in 1995, and the hole was later welded shut. What is left at the surface is a small rusted cap over a hole nine inches wide, in the floor of a ruined building. It must be the only place on Earth that is twelve kilometres deep and narrower than a dinner plate, and anyone who stands on it is standing on all of it at once.