This tower is as tall as that one. This picture is as beautiful as that one. Maria is smarter than Guido. There are a number of ways to compare two or more things in English, and the same is true for Italian.

Equality

Comparisons of equality, in which two Italian nouns, Italian adjectives, or Italian adverbs have the same characteristics, use the word pairs così...come or tanto...quanto:

Aldo è così diligente come Elena. (Aldo is as diligent as Elena.)

Luigi mangia tanto quanto Giorgio. (Luigi eats as much as Giorgio.)

Studiare è tanto difficilie quanto lavorare. (Studying is as difficult as working.)

When comparing nouns, the only the word pair tanto...quanto is used, and tanto must agree in number and gender with the noun it modifies:

Ho tanto denaro quanto tu. (I have as much money as you.)

Questo parco ha tanti alberi quanto l'altro. (This park has as many trees as the other.)

Voi scrivete tante lettere quanto mia sorella. (You write as many letters as my sister.)

Inequality

Not everything is the same, and you will need to know how to make comparisons of inequality too. Più...di and meno...di are the word pairs used to describe "more than" and "less than":

Marcantonio è più alto di Leonardo. (Marcantonio is taller than Leonardo.)

Gianni non è più intelligente di Francesca. (Gianni isn't smarter than Francesca.)

Stefano ha meno amici del ragazzo. (Stefano has fewer friends than the boy.)

Relative Superlatives

The relative superlative forms of adjectives in English may be distinguished by the words "least" or "most," or the ending -est. In Italian, you would use the definitive article, the word più or meno, the adjective, and the preposition di, as follows:

Lucia è la più brava della classe. (Lucia is the best in the class.)

Quella è la pinacoteca più grande di Firenze. (That is the largest art gallery in Firenze.)

Aldo è il meno svelto di questi ragazzi. (Aldo is the least quick of these boys.)