Without any doubt, the worst experience ever!
We live in Europe almost 5 years, and travel a lot, most of the times we bring our dog with us, and never had problem, anywhere in Europe. According to booking.com, this hotel accept pets, but once we checked in, we were told by the receptionist that we couldn't leave the dog alone in the room... which does not make any sense at all, but after offering to leave a deposit to cover any possible damage caused by our dog, the receptionist agreed to let the dog stay in the room while we were visiting Venice. When we were leaving the hotel for dinner, the manager showed up, and in a very rude way (raising his voice) told us that we could not leave the dog in the room. Since he was being horribly unpleasant, and threatening us, we decided to look for another hotel that allowed pets, to what we were told by the manager, that we could leave, but we still had to pay for the 3 nights we had booked! He claimed there is a law in Italy prohibiting anybody to leave a pet alone anywhere, because it could be interpreted as animal cruelty. If there is such a law, then it is totally misleading to advertise a hotel as pet friendly. Long story short, this "gentleman" almost ruined our whole vacation in Venice (which we had planned a year in advance), because we waisted a lot of time looking for another accommodation and paying a lot more money. By the way, even though we only stayed 1 night at Hotel Marco Polo we were forced to pay 50% of the total cost in cash, and they even tried to get the rest of the money by charging our credit card. I highly doubt this pet law exists, because we have been with our dog in Bellagio without any problem, but if it is true, then I think booking.com should warn its customers about this law in Italy.
Bottom line, Mr. Orlando Vermiglio, the hotel manager is in the wrong line of business, because he doesn't have the slightest idea about customer service or common courtesy.