This is the most popular restaurant I visited in Venice - we arrived just after it opened for the evening at 7:30 p.m. and barely got a table - on our way out the owner had to turn away several potential diners who didn't have reservations. The reason why Quattro Ferri is so beloved is not difficult to figure out - the food is fantastic and very inexpensive for Venice. We had one of the best pasta dishes I've ever had in Italy - porcini mushroom and giant prawn spaghetti for two people for only €17. The pasta was covered with freshly cut parsley, mushrooms and some ten giant prawns that must have been caught only a few hours before we ate them. Our table was situated close to the kitchen and thus we were able to see how they prepared our dish, which appeared to be the most popular that evening - the fact that the cook did very little with the prawns besides a quick fry and steam job merely indicates how fresh the prawns were and that the cook knew better than to mess with their natural flavour. As for the rest of the evening, a half litre of housewine was only €4 and the cover charge, which is quite often €2 per person, was only €1 here.
Practicalities: Ai Quattro Ferri is tucked away in an alleyway just off Campo S. Barnaba in Dorsoduro; Ca' Rezzonico is the closest Vaporetto stop on the Canal Grande. Drop by around lunch time to make a dinner reservation.