Rome's Piazza Navona

From "Walking Rome", a National Geographic guidebook:  "Piazza Navona is one of Italy's largest squares."  (Not to be taken literally, as you can clearly see.)  "Its oblong shapes relates to the stadium built here by Emperor Domitian in the late first century A.D.  The surrounding buildings, primarily from the 16th and 17th centuries, were sited on the footprint of the antique structures, whose ground floor now serves as their foundations."