I recently had a post about the importance of getting tickets to the Academia and Uffizi in advanced. It was a good thing I listened because they were close to sold out when I got them. Now I am wondering if there are any other musts of sights to get tickets to in advance.
I will be seeing the sights in:
London,
Copenhagen,
Prague,
Vienna,
Venice,
Florence (covered),
Rome,
Barcelona,
Paris