Campo de' Fiori Piazza historical timeline

A meadow, then a paved market, then the Church's execution ground, then a monument to one of the people it executed.

Chronology

1. Ancient Rome — the area is unused space between Pompey's Theatre and the flood-prone Tiber. Structural impact: nothing is built. What you see today: the reason an open rectangle survives in the densest part of the city.
2. Middle Ages — the name dates to the Middle Ages, when the area was a meadow. Turismo Roma gives the same origin: the square was made where a colourful field of flowers anciently stood. Structural impact: none. What you see today: the name.
3. 13th century — the Orsini establish themselves on the south flank of the space. Structural impact: one side acquires a palace. What you see today: the first building to define an edge.
4. 1389–1404 — the first church in the immediate vicinity is built under Boniface IX: Santa Brigida a Campo de' Fiori. With the building-up of the rione it now faces the part of the former square that is today Piazza Farnese. Structural impact: the square is divided by later development. What you see today: why the only nearby church faces the next square along.
5. 1440 or 1456 — the square is paved, and the sources differ. Turismo Roma: in 1440, with inns and hotels for pilgrims rising around the perimeter. The reference work: in 1456, under Pope Callixtus III, by Ludovico Cardinal Trevisani, as part of a large project to improve the rione Parione. Turismo Roma also credits the square's creation to Callixtus III, who reigned from 1455. Structural impact: a meadow becomes a surface. What you see today: the rectangle.
6. Later 15th century — with new access streets from Sixtus IV, Via Florea and Via Pellegrino, the square becomes part of the Via papale, the route linking St John Lateran and the Vatican, traversed by the Pope after his election in the Cavalcata del possesso. A horse market runs twice a week, Monday and Saturday. Structural impact: wealth, inns, hotels and shops. What you see today: the commercial character that never left.
7. 15th–16th centuries — the Taverna della Vacca, the cow's inn, still stands at the southwest corner, at the beginning of Via de' Cappellari. It belonged to Vannozza dei Cattanei, the most famous lover of Alexander VI Borgia, whose family seal is still on display on the house facade. Structural impact: none. What you see today: a Borgia coat of arms on a corner building.
8. 9 September 1553 — the Holy Office burns the Talmud here, following the Bragadin-Giustiniani dispute, on the first day of Rosh Hashanah. Structural impact: none. What you see today: a plaque in the market street, added in 2011.
9. 1590 — Giacomo della Porta makes a basin on the square. Because of the crowded market it soon becomes a sort of tub for keeping fruit and vegetables cool and washing them; papal edicts providing corporal punishment for repeat offenders are of little use. Structural impact: a fountain in the middle of a greengrocer's. What you see today: the behaviour, not the basin.
10. 17 February 1600 — Giordano Bruno is burnt alive for heresy in the square, and all of his works are placed on the Index of Forbidden Books by the Holy Office. Structural impact: none. What you see today: the exact spot, marked.
11. 1622 — the basin has to be closed with a large travertine lid, and Roman irony rechristens it Terrina, for its resemblance to a large soup tureen. On some feast days white or red wine of the Castelli spurts from its spouts instead of water. Structural impact: a lidded fountain. What you see today: the nickname, which outlived the lid.
12. 1624 — the body of the theologian and scientist Marco Antonio de Dominis is burned in the square. Structural impact: none. What you see today: that Bruno was not the only one.
13. 1659–1660 — the condemned women poisoners of the Spana Prosecution, including Gironima Spana, are executed here. Structural impact: none. What you see today: the square's working function for three centuries.
14. 1858 — the demolition of a block of housing enlarges Campo de' Fiori. Structural impact: the rectangle grows. What you see today: its present size.
15. 1869 — the market is placed here, having previously been held in Piazza Navona. Turismo Roma: it traditionally takes place every morning from Monday to Saturday. The reference work: a daily vegetable and fish market. Structural impact: the square acquires its daytime use. What you see today: the stalls.
16. 9 June 1889 — Ettore Ferrari's statue of Giordano Bruno is erected on the exact spot of his death; he stands defiantly facing the Vatican, regarded in the first days of a reunited Italy as a martyr to freedom of thought. The Terrina is evicted to make room for it and ends in the cobblestone depot at Testaccio, where it stays 35 years before settling in front of the Chiesa Nuova. Structural impact: a fountain out, a statue in. What you see today: the monument, and a fountain that is somewhere else.
17. 1898 — after a restoration, the square is given a new fountain reproducing della Porta's but without the famous lid. Structural impact: a copy replaces the original. What you see today: the fountain now used to keep cut flowers.
18. 2011 — a plaque commemorating the 1553 Talmud burning is affixed to the marketplace street, the idea inspired by the monument to Giordano Bruno. Structural impact: none. What you see today: the square's second memorial to a burning, 122 years after the first.