For romance, Bridge of Sighs is hit or miss.
The story is irresistible — condemned prisoners catching their last glimpse of Venice and freedom through the stone lattice, the 'sigh' a Byron-era romance — and the little white Baroque bridge over the Rio di Palazzo makes a pretty 30-second photo from the Ponte della Paglia. But manage expectations hard: this is a view, not a visit. You cannot walk it from the outside at all; the only way across is from inside the Doge's Palace, where you cross it almost without noticing on the route from the doge's apartments to the old prisons. Photograph it free in passing, but the experience itself lives inside the palace — don't make a special trip of the exterior.