At 110 acres, the Vatican City is the smallest independent state in the world, but it compensates with overstuffed museums and the papal complex around St. Peter's Square. Step inside its medieval and Renaissance walls to marvel at Michelangelo's Sistine Chapel frescoes and St. Peter's Basilica, the seat of the Roman Catholic Church. A climb to the top of the basilica's dome affords expansive views of Rome. To avoid the lengthy lines, try a guided tour or visit in the afternoon.