Work began on this European cathedral in the 14th century, yet its unique spires—characterized by a variety of architectural styles, including Neoclassical, Gothic Revival, and Art Nouveau—weren't completed until the 19th century. Can you guess where this is?

Log in and leave your guesses below and be sure to check back on Monday for the correct answer.

UPDATE 3/21/11: T+L community members sholverson, aldaformenti and MoniquePellerin all guessed it right! This is indeed the Duomo di Milano, or the Milan Cathedral, in northern Italy. We're going to have to make these harder for you guys. Check back this Friday forthe newest edition of "Guess Where?"

Lyndsey Matthews is an online editorial assistant at Travel + Leisure.