Reservations for St. Mark's Basilica?

October is still high season in Venice, and especially crowded when there are cruise ships in (which is almost every day). We like to reserve a time during the period when the mosaics are lit, which was 11:30 - 12:30 the last time we were in Venice (October 2015).

You can probably wait and reserve your time the night before if you want, so as to maintain some flexibility. That's what I did (in June) and I had no problem getting a time between 11:30 and 12:30 (and, yes, the lights were on).

One option you may want to consider is Walks of Italy combined tour of Doge's Palace and St. Mark's Basilica. We found it invaluable in skipping the lines and having maximum focus/efficiency in seeing the important artifacts within each venue. Their english-speaking tour runs daily from 2-5p, and is limited to small groups (ours capped at 6 people, it might be as many as 8 during off-season/October) which makes for ideal mobility and interaction with the guide. The conclusion of this tour puts you on the balcony of the church which offers an amazing viewpoint of the plaza and its two-column gate fronting the harbor.

Were were there last month (June 26-28) and our hotel advised us to wait until 4:00pm to visit St. Mark's. We had a very short, 5-10-minute wait outside and went right in. If you're there overnight, go out early (7:30-8:30am) and just walk around and through the square...you'll almost have it to yourselves. You are wise to have your museum tickets in Florence booked. I would also book dinner reservations in Florence, btw. Enjoy! We loved Venice!