Palazzo Zuccari, Rome, Italy

Fearsome façade. Palazzo Zuccari, Rome

At the top of the Spanish Steps in Rome, take a left underneath the imposing Catholic church. Down an unassuming side street, there's a surprise waiting for you: a house of monsters. Welcome to the Palazzo Zuccari, a 16th-century palace where myths seem to come to life on its façade—grotesque faces swallow up its doors and windows. Federico Zuccari, who built the palace, was well-versed in monsters. His painting of the Last Judgment in Florence Cathedral and his illustrations of Dante's Inferno are replete with mythical beings. The monster door originally led to the palazzo's garden because Zuccari enjoyed making his guests experience the contrast between the scary entrance and the beautiful serenity of the garden. These days, the door leads to the Bibliotheca Hertziana, a library specializing in Italian art history, from the Middle Ages to the modern day, which has occupied the site of the garden since 1912.

If you're looking for more monstrous mouths in Rome, not far from the Palazzo Zuccari is the Bocca della Verità, an ancient Roman mask. According to legend, it will bite off any liar's hand that's placed in its mouth.