In 1563, an eighty-eight-year-old Michelangelo performed his final act of transmutation: raising a basilica inside the intact frigidarium of the Baths of Diocletian, converting the largest pagan bathing hall of antiquity into a Christian vessel without demolishing a single Roman vault.
Across its transept floor runs the Linea Clementina: a 45-meter bronze solar meridian commissioned by Pope Clement XI and laid down in 1702 by astronomer Francesco Bianchini. A pinhole aperture 20.34 meters up in the south wall projects the solar disc onto the bronze line at local noon, flanked by marble inlays of the zodiac. The Church built it to fix the true date of Easter — and, quietly, to prove Rome could measure the heavens as finely as any Protestant observatory.
The full decipherment and its observational protocol — where to stand, when, and what to watch for — are in the Rome field codex.
Or read the complete Florence codex free first.