We visited Vatican City during our trip to Italy in May of 2014. You can read more about our trip to Italy HERE.
Sadly, our visit to the Vatican wasn't as amazing as it could have been and it had everything to do with the tour guide we were assigned. Despite the crappy tour, seeing the Vatican was amazing. Half way through the tour we decided to part ways with our group and escort ourselves the rest of the way. The highlight of course was seeing the Sistine Chapel where in lies the ever famous ceiling mural by Michelangelo.
After seeing images of the mural in books and online my entire life, seeing it in person was almost magical. Having been raised Catholic, it was very cool to stand in St. Peter's Square where people gather to hear the Pope speak. We even peeked down the driveway where the popemobile enters and exits.
The Vatican is most certainly a popular tourist attraction so be prepared to wiggle your way through crowds both inside and out. The lines were very long as well, but we skipped to the front because we made online reservations with our tour. While our tour guide was less than expected, we did hear wonderful things from friends who visited before us and still recommend making reservations for a tour. At the very least, you'll save yourself an hour of standing in line.