Multiple choice What is "unique" about the Leaning Tower of Pisa? It was purposefully built to have a 5.5 degrees It is hollow It is the 3rd largest tourist attraction in the world Galileo and Aristotle held public debates on the 4th floor Reveal answer Fill a bubble to check yourself B Correct answer Explanation The Leaning Tower of Pisa is constructed with a hollow center, which is a notable architectural feature given its height and the instability of the ground it sits on.