Athens is the capital of Greece. It has a population of around 3.7 million people.
Contact lenses are small pieces of soft plastic gel that can be worn directly on your eyes instead of glasses.
A lens is a device that changes the way light bends. When you look through a lens things look different to when you don't look through the lens. Lenses can be used to make things seem closer than they are, or in spectacles to correct poor vision.