8) Colosseum

Colosseum is a surviving structure of imperial Rome. Constructed in 70 AD it was used for gladiator fights and other exotic spectacles, and could seat 80,000 people according to some estimates. This elliptical amphitheater is built of concrete and stone and is a classic example of Roman architecture.

7) Mount Rushmore National Memorial

This monument depicts the faces of past US presidents George Washington, Thomas Jefferson, Theodore Roosevelt and Abraham Lincoln. Located near Keystone, South Dakota, it is a sculpture carved into the granite face of Mount Rushmore.