Is la longitud right?

[Neophyte]

I have this nagging question that I cant get resolved. What is the best way to talk about the length of something?

El largo de x
La largura de x
La longitud de x

?

[sosia]

Spain:
La longitud del trayecto era de 10 km.
La longitud de este rectángulo es 3m de alto y 5m de largo
Not so often heard: El alto de este rectángulo es 3 m y el largo es 5m.
for us, largo is adjective
Este barco es muy largo. El largo invierno.
largura is used, but no is not so common as in Mexico ( ask tomisimo)
Era generoso con largura (literall He was very generous in a long way: He was very generous)
Este vino tiene largura (literall: This wine "has long":this wine's flavours persist in the mouth)

[Neophyte]

So I take it "longitud" is the best way to talk about length in a literal way, as in the length of an object.

About "largo", I know it's an adjective, I'm positive I've heard people use it as a noun too. As in "el largo de X" talking about the length of it, but maybe I'm wrong.

[sosia]

in my reply I said
"Not so often heard: El alto de este rectángulo es 3 m y el largo es 5m."

so saying "el largo de esta mesa es 2m" is ok, but its better to say "esta mesa tiene 2m de largo"

Greetings