Diamond Head is a direction

I love directions on Hawaii! It is hard to tell which way is North because the island is odd shaped and not set on an axis. But it is easy to tell if you are headed for towards the mountains or the sea. So those are the directions: makai is toward the sea and mauka is towards the mountains.
This sign in the Ala Moana parking lot tells me my car is on the side nearest the mountains (mauka). See, there are the mountains!
In Honolulu, the other two directions are towards Diamond Head or towards Ewa (which used to be a plantation so has been a landmark for a long time before it turned into a neighborhood). So, the sign also says my hypothetical car is on the side towards Diamond Head (easterly).
The food court doors also tell you which side of the mall you are on.
This directional sign is on campus near the law school. It points to the mountains. The other side points west-ish.

"Diamond Head" or "Eva" don't really make sense outside Honolulu but mauka and makai are used everywhere. "Kai" means ocean so it is part of many words in Hawaii.