The tiny sovereign state of the Vatican is an essential stopover on any Roman holiday and offers enough in itself to fill days if not weeks. Consecrated in 1626, the current St. Peter's Basilica remains the symbol and heart of the Catholic church and houses Michelangelo's stirring Pietà and Bernini's spectacular tomb of Pope Alexander VII. Bernini is also responsible for the magnificent elliptical colonnade in St. Peter's Square.
If you are up for the climb (and don't suffer from vertigo), take the steps up to the top of the dome for incomparable views—and a much welcome bar-café.