Yes, the word mundo (world) has several interesting idioms. Let’s check out some of them, shall we?

medio mundo – a lot of people.
Medio mundo estaba en la fiesta.
A lot of people were at the party.

caérsele / venírsele el mundo encima (a alguien) – (someome) to suffer from a severe letdown or disappointment, (someone’s world) to fall apart.
Cuando le dijeron que estaba despedido, se le vino el mundo encima.
When he was told he was fired, his world fell apart.

desde que el mundo es mundo – for a long time, since time began.
Desde que el mundo es mundo las mujeren han ayudado a los hombres a tener éxito.
Since time began women have helped men to be successful.

el mundo es un pañuelo – it’s a small world.
El mundo es un pañuelo, no esperaba verte aquí.
It’s a small world, I didn’t expect to see you here.

hacer un mundo – to make a mountain out of a mole hill.
De cualquier cosa haces un mundo.
You make a mountain out of a mole hill with anything.

hundirse el mundo – (a catastrophe) to happen.
Si no se hunde el mundo, nos vemos en Argentina el año que viene.
If nothing bad happens, we’ll see each other in Argentina next year.

ponerse el mundo por montera – to do something bold, to do something risky.
El director de la escuela se puso el mundo por montera y admitió a varios niños africanos a pesar de las protestas de los padres.
The principal was bold and admitted several African kids into the school despite parents’ protests.

por nada del mundo / (ni) por todo del oro del mundo – not for anything in this world.
El abuelo no se iría de su pueblo por nada del mundo.
The old man wouldn’t leave his town for anything in this world.

tener mucho mundo / ser de mundo – to be very experienced.
Como tiene mucho mundo, no es fácil que le engañe.
As he’s very experienced, you can’t fool him easily.

Por hoy es todo, nos vemos prontito.