Guided tour of St Mark's and Doge's Palace

Also, how do you get to go up the Bell Tower?

For the bell tower...just stand in line and take the elevator up! If you can somehow judge the line (and look into when the bells ring) we actually, thru no trying on our part, were up top the bell tower when the bells started ringing - loud and amazing, one of my fav memories...I used my camera to do a video - it was also funny to see the looks on the faces of the people who did not notice the bells start swinging - once that 1st gong struck...I would hazard a guess they ring every hour thru the day, but not sure

There are Rick Steves audio tours for them (the Square, the Basilica and the Palace) and for the Grand Canal by vaporetto. The best time to be in the Basilica is between 11.30-12.30, when the mosaics are floodlit. You can download all the RS audio tours at iTunes. There are also tours for your sites in Rome.

I recommend the doge's palace secret itineraries tour. Very informative on how Venice worked for hundreds of years. We used the book and podcast i think for the st. marks basilica on our own and that was plenty. Some in our group even went to confession at the church!

Other than a private tour guide, I am not aware of any tour that combines the two. When we were there earlier this month, there weren't any tours in English offered for St. Mark's. (Despite what we found in two different guide books) The only tour I know of for the Doge's Palace is the Secret Itineraries tour. As someone else mentioned, you can get Rick's Audio tour. There are also PocketVox audio tours that I have seen recommended elsewhere, but have no experience with.