There have been recorded cases of people gazing upon a beautiful panorama of Florence or an exquisite painting and suddenly collapsing. The condition is known as Stendhal syndrome, alternatively called Florence syndrome or hyperkulturaemia (excess culture in blood). It has been described as causing tachycardia (rapid heartbeat), dizziness, confusion and fainting after being exposed to a particularly beautiful piece of art or scenery. It is named after French author Stendhal (penname of Henri-Marie Beyle), who upon visiting Florence in 1817 experienced the very condition.
Stendhal syndrome is most likely related to a very common phenomenon known as vasovagal syncope, where extreme emotions overwhelm the brain, induce a massive parasympathetic nervous response, causing the person to faint. There are two major nervous systems: the sympathetic and parasympathetic. The sympathetic nervous system is responsible for the fight-or-flight response and essentially prepares the body for physical activity. The parasympathetic nervous system does the complete opposite and is activated when you are resting or digesting food. Thus, a burst of parasympathetic nervous activity causes a sudden fall in heart rate and blood pressure, causing the brain to lose the oxygen supply needed to maintain consciousness. When the person faints, they collapse and blood flow is restored to the brain. Vasovagal syncope can be caused by anything from standing up very quickly, extreme emotions (e.g. stress, seeing blood or needles) and fatigue. It is the most common cause of collapse and is (usually) completely harmless.
When a person looks at a breathtaking view or a stunning work of art, their brain is overwhelmed by intense emotions of excitement and joy. In the case of Stendhal syndrome, this effect is so great the person is literally blown away by the sight.
The people of Florence have noted that this phenomenon is rather common in tourists visiting the beautiful city.