Roads are not flat. There is a crown in the middle and they slope down to each side so water does not pool.

For centuries, stages were “raked,” which is to say they sloped towards the audience to make it easier to see action at the rear of the stage. After hundreds of years, someone noticed the rake made sets fall down and required sawed off legs on chairs. So the rake has fallen out of style.

For much of the 20^th century, the ground floor in a movie house was flat, because it was cheap. Some began to rake the seats, a gradual slope up to the back. Most modern cinemas have what is called stadium seating (after the sporting venues), with a more pronounced rise.