Learn Portuguese (Portugal): O lugar é bonito.

In Portuguese, there are two verbs for "to be": ser (for permanent things) and estar (for temporary states). Because being beautiful is seen as a permanent, built-in characteristic of the place, we use é, which comes from the verb ser.

How can I tell that lugar is a masculine word since it doesn't end in "-o"?

While many masculine words end in "-o", words ending in a consonant like "-r", "-l", or "-z" are often masculine too. The biggest clue in this sentence is the word right before it: the masculine article O (the). Because the noun is masculine, the adjective at the end must also take the masculine form, bonito.

If I wanted to say "The places are beautiful", how would the word lugar change?

To make a word plural that ends in a consonant (like the "r" in lugar), you add "-es". The plural is lugares. The rest of the sentence must also become plural to match, resulting in: Os lugares são bonitos.

I've also learned the word lindo. Could I use that instead of bonito?