For about two weeks before Lent the city fills with elaborate 18th-century masked costumes, the Piazza hosts the 'Flight of the Angel' and free shows, and you can watch (or, at a price, join) candlelit masquerade balls — at its best it's genuinely otherworldly. The catch: it's the most crowded, most expensive, coldest, dampest fortnight of the year (acqua-alta season), private balls cost a fortune, and the daytime square can feel more photo-mob than magic.