Learn Italian: La parte turistica è affollata. - The touristy part is crowded.

Nouns ending in -e can be masculine or feminine in Italian. Parte happens to be feminine, which is why it uses the feminine article la and the feminine adjectives turistica and affollata.

How would I change this sentence to say 'The most touristy part is crowded' using the relative superlative from this lesson?

You would add più before the adjective. The sentence would become La parte più turistica è affollata. Because the definite article La is already at the beginning of the noun phrase, it combines with più to form the relative superlative (the most touristy).

If we were talking about plural parts, how would turistica change?

It would become turistiche. Feminine adjectives ending in -ca add an h in the plural to keep the hard 'c' sound, so the full phrase would be Le parti turistiche sono affollate.

Is affollata related to the Italian word for crowd?

Yes! It comes from the noun la folla, which means the crowd. As an adjective in this sentence, it ends in -a to agree with the feminine singular noun parte.