Let's be real here: you and I along with almost everyone else are here for the Sistine Chapel.
Nothing wrong with that! After all, Michelangelo's Sistine Chapel fresco (http://www.yelp.com/biz/cappella-sistina-roma?hrid=eXRIJHaIaaQ2PaMDFNvzZQ) is perhaps the world's most famous artwork and thus the headliner of Musei Vaticani (Vatican Museums). However, on your rush to the famous chapel fresco, don't miss out the rest of this enormous museum collection. One of the world's largest, Musei Vaticani are so huge that it's in plural form, with their corridors literally extending for miles (or kilometers in local unit)!
Inside this impressively huge museum(s), the collection spans from antiquity to modern arts. Although not as stunning as the Sistine Chapel - very few things are - other highlights in Musei Vaticani are worth seeing!
1) Gallery of Tapestries: Walk through the hallway lined with lavish tapestries that once covered the lower walls of the Sistine Chapels. These tapestries were done by Flemish masters with the design by the workshop of the Renaissance master Raphael.
2) Gallery of Maps: What other way to brag about your vast territories than having map fresco on your wall? Awe at not only at the extricate maps on the side but also the beautiful ceiling that adorns this hall of fame!
3) The Raphael Rooms: Perhaps my favorite besides the Chapel, this papal apartment is filled with colorful fresco by Raphael and his assistants. In this fine example of Renaissance room decor, you can find one of Raphael's best works, "The School of Athens"
4) Bramante Staircase: However, aside from the Chapel, this intriguing helix staircase at the exit is another headliner of Musei Vaticani
Unfortunately, during normal hours during peak season, expect to be packed for sardines especially if you are in the direct path between the museum entrance and the Sistine Chapel like the Gallery of Maps, which becomes even more unbearably crowded itself. Clearly, Musei Vaticani corridors were designed as a private gallery for a small group of exclusive audience...
I highly recommend you paying extra for either early access or late-night opening to enjoy this museum like it's a museum instead of a flea market. Especially in the summer heat, the crowd can get ridiculously huge and you will not have the time or the space to admire anything, even in the famed Sistine Chapel. If you don't want to pay extra, at least reserve the ticket online so you can skip the notoriously long line.
Overall, Musei Vaticani is a must-visit for all Roman visitors, especially because of the Sistine Chapels, but it can be a major headache without advanced booking. Unless it's an off-season, expect this museum visit to be a purely sightseeing venture rather a cultural experience.
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TIPS TO ENJOY THE MUSEUM
1) Book early-access or late-night tickets either through official website or private tour groups to avoid the crowd
2) If Option 1 is no go, reserve your ticket via the official website to skip the line
3) All tours start in the morning, so the crowd may be lighter in the afternoon but note that the Sistine Chapel and Pinateocha close earlier than the whole museum
4) Enjoy a light snack in the cafe, because this is one of the only two places you can dine in the Vatican City premise! (Other being the rooftop cafe atop of St. Peter's Basilica)
5) If you want to visit the Basilica afterwards, sneak out the "secret" group tour passage on the right of the Sistine Chapel to skip the line! Nobody can and will filter you out of the constantly moving crowd. Note that you will miss out the spiral staircase by exiting this way though.
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tl;dr version:
1) Impressively huge museums with the Sistine Chapel
2) Ridiculously packed especially during normal hours at peak season
3) Highly recommend booking early access or late night opening read more