[3] A traveler in 1819 remarked that during Twelfth Night celebrations in Rome the Piazza della Rotonda was "in particular distinguished by the gay appearance of the fruit and cake-stalls, dressed with flowers and lighted with paper lanterns.

"[4] Charlotte Anne Eaton, an English traveller who visited in 1820, was much less impressed with the piazza and deplored how a visitor would find himself "surrounded by all that is most revolting to the senses, distracted by incessant uproar, pestered with a crowd of clamorous beggars, and stuck fast in the congregated filth of every description that covers the slippery pavement ...

Nothing resembling such a hole as this could exist in England; nor is it possible that an English imagination can conceive a combination of such disgusting dirt, such filthy odours and foul puddles, such as that which fills the vegetable market in the Piazza della Rotonda at Rome.

The Aqua Virgo, one of the eleven aqueducts that supplied ancient Rome with drinking water, served the area of the Campus Martius, but had fallen into disrepair and disuse by the late Middle Ages.

In 1570, Giacomo della Porta was commissioned under Pope Gregory XIII to oversee a major project to extend the distribution of water from the Vergine to eighteen new public fountains.

The obelisk, originally constructed by Pharaoh Ramses II for the Temple of Ra in Heliopolis, had been brought to Rome in ancient times where it was reused in the Iseum Campense, a shrine to the Egyptian god Isis that stood to the southeast of the Pantheon.