St. Peter's Square historical timeline

An Egyptian obelisk, moved twice, with a Baroque square eventually built around it.

Chronology

1. Ancient Egypt — the obelisk is erected at Heliopolis by an unknown pharaoh. Structural impact: a single piece of red granite over 25 metres long is quarried and raised. What you see today: the shaft at the centre of the square, with no hieroglyphs on it.
2. 1586 — the obelisk is moved to its current site by the engineer-architect Domenico Fontana. Structural impact: the centre of the future square is fixed, eighty years before the square exists. What you see today: everything else arranged around it.
3. 1613 — Carlo Maderno designs a fountain for the space. Structural impact: a second fixed point, off the central axis. What you see today: the northern fountain of the pair.
4. 1656-1667 — Turismo Roma records eleven years of work on Bernini's colonnade: 284 columns set radially in four rows, giving the square its elliptical form. Structural impact: the forecourt becomes an enclosed oval with two arms reaching toward the city. What you see today: the colonnade — though see the next entry.
5. 1667-1676 — the reference work instead dates the redesign of the open space before the basilica by Bernini to these years, and counts 248 columns and 88 pilasters with 140 over-lifesize saints on the cornice. Structural impact: the same structure, differently dated and differently counted. What you see today: one colonnade and two accounts of it.
6. 1675 — Bernini builds a granite fountain to match Maderno's. Structural impact: the square gains its symmetry across the short axis. What you see today: two fountains, made sixty-two years apart, that read as a pair.