Pontifical Sanctuary of the Holy Stairs (Scala Santa) historical timeline

A staircase that was moved twice, cased in wood for three centuries, and may still only be climbed one way.

Chronology

1. c. AD 326 — by tradition, the Empress Saint Helena, mother of Constantine, brings the stairs from Jerusalem to Rome. They are believed to be the stairs Jesus climbed in Pontius Pilate's palace. Structural impact: twenty-eight marble steps arrive in the city. What you see today: the steps themselves — the reference work is careful to call this a medieval legend.
2. Under Nicholas III — the Sancta Sanctorum, the Chapel of San Lorenzo in Palatio, receives its 13th-century frescoes and Cosmatesque floor. Structural impact: the popes' private chapel is fitted out. What you see today: the floor and the painting behind the grille.
3. 1589 — Pope Sixtus V has the stairs moved to the current building, reconstructed before the Sancta Sanctorum, with Domenico Fontana designing four flights around the central Scala Santa. Structural impact: the sanctuary is purpose-built around one staircase. What you see today: five parallel flights, and SIXTVS V FECIT carved across the front.
4. 1724 — Pope Benedict XIII covers the marble stairs in wood for their protection. Structural impact: the surface that pilgrims touch is no longer the surface itself. What you see today: see the next entry.
5. 2019 — the protective wood covering is removed and the marble exposed following restoration work, after nearly three centuries. Structural impact: the original stone is uncovered. What you see today: neither source states what is in place now, so expect either.

• Official website
• Wikipedia