I love the Venetian replica of the Piazza San Marco. I had eaten at Canaletto for dinner my last trip and it was such a wonderful experience that I went back this trip too. However, this time I had lunch...and it wasn't that great.
The ambience is wonderful no matter what time you go though and I highly suggest sitting on the patio so you can people watch. I realize people watching in Vegas is amazing no matter what but wedding parties frequent this area as some actually get married riding the gondolas in the Canal. There are also singers and mimes in the Piazza that are fun to watch.
I assumed they would have a different menu for lunch or even a brunch menu...but no, same menu all day. They only have heavy meats and pastas so I couldn't find anything I really wanted. Plus my girlfriend ate a huge pasta dish and had to take a nap afterwards! Lunches that make you want to nap are not good in Vegas!!