Begun in 1173 as the cathedral bell tower, Pisa’s campanile started tilting due to weak subsoil and shallow foundations. Over centuries, the lean increased until a late‑20th‑century stabilization campaign (soil extraction, cable anchoring) reduced tilt by ~40 cm. Today the tower stands safely, a case study in geotechnics, heritage risk, and public fascination.
Part of Pisa’s Piazza dei Miracoli ensemble with cathedral and baptistery, the tower’s circular plan carries colonnaded arcades. Differential settlement began by the third storey; builders paused repeatedly to adjust courses and mitigate tilt.
Eight storeys including the belfry crown the 56 m height. Limestone and marble rings with rubble cores are bound by mortar; spiral stairs thread the thickness. Seven bells, retuned over time, once regulated civic rhythms.
An international committee closed the site in 1990. Measures included temporary lead counterweights, a concrete ring beam, anchored cables, and crucially, carefully monitored soil extraction (under‑excavation) from the north side to nudge the tower upright. Tilt was reduced to about 4 degrees and the structure reopened in 2001.
Inclinometers, crack gauges, and ground sensors track behavior; periodic maintenance addresses water ingress and stone decay. Visitor numbers are capped; timed slots regulate climbs.
Book ahead for the climb; late afternoon light flares the marble arcades. Explore the cathedral museum for context on the ensemble’s art.
