Beneath the surface Sudbury has the richest nickel deposit on the planet; when a comet hit planet earth as a meteorite 1.8 billion years ago, it created a huge crater. The powerful impact melted rocks into magma filled with minerals including nickel. The nickel deposit was discovered while workers were blasting rock here in 1883 for the building of the transcontinental Canadian Pacific Railroad. The new industry transformed the city and polluted the air. Tunnels spread below the surface in every direction and the Creighton mine is 2 kilometers deep. The Sudbury Neutrino Observatory, one of the most advance physics laboratories in the world, is in a specially excavated section of this mine where the rock shields it from cosmic radiation. SNOlab is conducting a search for dark matter, the mysterious substance that seems to make up 85% of the matter in the universe. Sudbury's famous Big Nickel landmark celebrates mining history as well as scientific progress.