Vatican City
Just had time today to see the museum and Chappell. It was definitely worth the price (20 euro). You can spend all day there! Audio book is 8 euro extra. Please be reminded shoulders and knees must be covered for women! I opted to bring a pair of pants in my bag and change into them once I was ready.
Ps you can also stand in line for tickets if you forget to book. I went around 1:30pm and the line was about half way to the end of the block (maybe more) waited 1.5 hours and was in!