The Great Wall of China Actually consists of numerous walls- many of them parallel to each other - built over some two millennia across nòrthern China and southern Mongolia.
the most extensive version of the wall runs for some 8,850 km east to west. Although lengthly sections of the wall are now in ruins or have disappeared completely, it is still one of the most remarkable structures on Earth. **
** It was built to protect the country from mongol invaders. It is one of the largest building construction projects ever undertaken 