Learn Italian: Mio nonno guarda con stupore questo quadro magnifico. - My grandfather looks at this magnificent painting with amazement.

You would use Che (what a) followed directly by the noun and adjective: Che quadro magnifico! Notice that unlike English, Italian does not use an article like 'a' or 'an' after che in exclamations. You could also use Quanto: Quanto è magnifico questo quadro! (How magnificent this painting is!).

Why is it just Mio nonno and not Il mio nonno?

In Italian, you must drop the definite article (like il or la) before possessives when talking about singular, unmodified family members. Since nonno is a singular family member, it is just Mio nonno. If it were plural, you would need the article: I miei nonni.

The translation says 'looks at', but I don't see a word for 'at' in Italian. Why not?

The Italian verb guardare inherently means 'to look at' or 'to watch'. It connects directly to its object without needing an extra preposition. So, guarda questo quadro perfectly covers 'looks at this painting' all on its own.

Is con stupore the only way to say 'with amazement'?