Cork comes from a tree called the cork oak. This tree grows wild around the Mediterranean Sea, and has been cultivated in Portugal, Spain and North Africa. The cork is actually the thick spongy bark of the cork oak. The cork is harvested carefully to avoid killing the tree - it is stripped away from the lower trunk, then left to grow back for about 10 years before the next harvest. Cork is used to make many things from bottle corks, to pin-boards and floor tiles.