"Lo" instead of "El"?

Question

"En el mundo hay muchos paises interesantes pero para mí, el más interesante es Australia."

My question is, why is could one also say "lo más interesante..." and still be correct? That is, use "lo" instead of "el"?

Accepted Answer

Hola Pati
Using "lo más interesante" here would be incorrect because we a a reference in this sentence which is a masculine thing "el país/los países", therefore you need "el más interesante" (the most interesting [country]). 
To use "lo más + adjective" we need to be referring to a neutral idea or to "the most interesting thing about something" as a neutral thing. For example:

Ayer vi una película y me gustó mucho. Lo más interesante fue el final, cuando los protagonistas se encuentran de nuevo...
Yesterday I watch a movie and I loved it. The most interesting [thing/part] was the end, when the main characters meet again...

Here is a lesson using "lo" where you find some examples (by the end of the lesson) with this same structure. I hope it helps.
Saludos
Inma

Answer

Because el país is masculine and "el más interesante" refers to the country. If, on the other hand, if no  subject was not mentioned then "lo que "could be used.Esto es lo más bello del pais.

Answer

Okay. Thank you very much for the explanation. I get it now. Pati Ecuamiga

Answer

En mi familia, yo soy la más vaga.In my family, I am the laziest.May I know how do I know the masculine and feminine here?Is modern style consider masculine and when car and house also?

Answer

Todavía no entiendo cuál  es la diferencia entre lo más y el más

Answer

Hola Carol,
with "el más ..." we have a clear and specific masculine referent in the sentence, for example:

Tengo muchos amigos guapos pero el más guapo es Miguel.
I have lots of handsome friends but the most handsome one is Miguel.

Here you have a clear masculine noun that is the referent to "el más" (amigos)
But look at this other sentence:

Me divertí mucho en Málaga; lo más divertido fue ir a la playa.
I really enjoyed myself in Málaga; the most fun thing/part was going to the beach.

Here there is no clear referent for "lo más"; we are using "lo" because it is referring to the most fun "thing" as something neutral/ an idea.
Saludos
Inma