Venice - St. Marks Cathedral and Academia Gallery

The ticket line at San Marco was running about 30 minutes long when I visited Venice in late September. I fired up my smartphone and checked the website, but there were no tickets available for immediate entry. (There may have been some for later in the day; I simply don't remember.) Therefore, I wouldn't suggest waiting until the morning of the day you want to see the church to buy the ticket unless you're OK with the back-up plan of just getting in the ticket line. (It will be long, but it moved surprisingly fast for me.) Obviously, demand for tickets can vary by day and hour, but I've never heard that you need to get this ticket very far in advance. It's just a matter of avoiding the need to wait in the ticket line for what is, in the context of heavily-visited European cities, not typically all that long.

There are a number of ticket options at San Marco. I found the Pala d'Oro and the museum both worthwhile. The museum gives you a closer view of the wall mosaics, access to the viewing terrace overlooking the piazza and the opportunity to get up close and personal with the original horses. The Treasury was still closed at the time of my visit, I assume because it's small and there remains concern about crowding. I don't know of any reason why you couldn't wait and pay for the add-ons after you arrive; that's what I had to do, because when you buy the ticket for the church at the door, there is no option to pay for the additional entries at the same time. The ticket counters for the Pala d'Oro are easy to locate since there's basically a one-way path you take through the church.

I'd suggest going to the ticketing website (https://basilicasanmarco.skiperformance.com/en/store#/en/buy) from time to time in the week or so leading up to your visit. You'll be able to see how many tickets remain available for each time block. The first ticket time is usually quite popular at busy sights, because it means you walk into a place with no holdover visitors. But the mosaics are illuminated around the middle of the day, and many people like to see them at that time.

The Accademia in Venice, unlike the museum of the same name in Florence, doesn't seem to get slammed with visitors. I just walked up and bought a ticket. I suppose there might be occasions when you'd run into a line, but I didn't. As with San Marco, you can check the website (https://gallerieaccademia.eventim-inhouse.de/webshop/webticket/timeslot) periodically to be sure there's no shortage of tickets for the date(s) and time(s) of interest to you. As of this moment (roughly opening time on Tuesday at the museum) it appears tickets are available for all time periods for the remainder of the week.

You didn't ask about the Guggenheim. It was busier than the Accademia in September. I doubt that tickets need to be purchased far ahead of time, but the first time I walked by the museum, there must have been 20 or 30 people in line, and I wasn't sure whether they were waiting to buy tickets or were ticketholders waiting for their entry time. At that point I decided it made more sense to buy a ticket for a future date, something I was free to do because I was in the city for a good while. On a short visit, I'd recommend monitoring ticket availability at the Guggenheim if you want to see it (it's very, very good if you like modern art). That way you can grab a ticket if things begin to tighten up. The website is https://www.guggenheim-venice.it/en/visit/

When I was there last month, I visited both.

I decided I didn't want to wait in the line at St. Mark's. This was around noon, I think. It was sold out for the rest of the day and most of the next, but I was able to get 3:30PM the following day. If you book 2 or 3 days ahead, there will be much more availability.

For the Academia, I walked in and was second in line, so no need to pre-book that one. It was very worth time, and I appreciated having the audio guide.