Piazza San Pietro
This is the large public square outside Saint Peter's Basilica, which is considered the greatest church on Earth. The square is actually round, with the perimeter marked by two huge colonnades. The roofs of these colonnades are supported by four rows of Doric columns 60-feet tall. The ellipse symbolizes Saint Peter's, the mother church of Christianity, embracing the world. At the center of the square is an Egyptian obelisk brought to Rome by Caligula in 38 from the town of Heliopolis, on the Nile Delta.
It was part of Nero's Circus where Saint Peter was crucified, and where construction on Saint Peter's began in 324. The obelisk was moved to its present location by Pope Sixtus V. While being positioned it almost fell over. A warning cry from a sailor saved the 85-foot-tall artifact from toppling and shattering into millions of pieces. To this day the palms for Palm Sunday are brought to the Vatican from the sailor's home town of Bordighera to reward his attention. At the top is a "Chigi Star" in honor of Pope Alexander VII, a member of the Chigi family who oversaw the building of the piazza. The obelisk is flanked by two fountains, and halfway between the fountains and the obelisk are stone circles in the ground. If you stand on one of the circles, you can see an optical illusion -- the four rows of 60-foot tall pillars forming the colonnade disappear behind each other and look like a single row. The piazza has to be large to accommodate the throngs that show up at noon on Sundays and several other times each week to hear the Pope say mass and to receive his blessing. As it is now, the square can handle about 300,000 people but has been known to pack in more. The Pope delivers his blessing from a library window overlooking the square. You can approach the square, Saint Peter's, and the Vatican as a whole by coming up the Via della Conciliazione. Two rows of houses were demolished by Mussolini in 1936 to build this boulevard from Piazza San Pietro across the Tiber River to the center of Rome. This was Mussolini's symbolic way of honoring the "conciliation" between the Vatican and the Italian government. The Vatican is an independent country since 1929 with its own army (supplied by Switzerland), airport (actually a helipad), train station, radio station, currency and postal service. The Vatican money is legal everywhere in Italy, and the Vatican postal system is more reliable than the Italian postal system, so if you're mailing something back home, bring it by Saint Peter's Square.