Egyptian Obelisk Rises From Bernini's Fountain of the Four Rivers, a photo by freshEIRE on Flickr.
The piazza was built upon the site of an old Roman circus constructed by Domitian in AD 86. In the 15th century it was paved over and has served as a public market since.
Olimpia Maidalchini (born on 26 May 1591 – died on 27 September 1657) was the sister-in-law of Pope Innocent X . However, despite this power and prestige, Rome had no love for the woman whose greed and ruthlessness included theft of church property and the poisoning of cardinals to further her own political agenda. Now it is said her vile apparition can be seen racing through Piazza Navona, laughing hysterically.