The Leaning Tower of Pisa

Key dates in the history of the Tower of Pisa.

1173: Construction begins. 
1178: Construction is halted. 
1272: Construction resumes. 
1278: Construction is halted again. 
1298: The first commission to study the Tower's lean is convened. 
1370: Construction officially completed. 
1838: Architect Alessandro della Gherardesca excavates a walkway around the Tower, flooding the base of the campanile and destabilizing the structure. 
1934: Italian dictator Benito Mussolini sanctions a plan to inject 90 tons of cement into 361 holes at the base, which nearly topples the Tower. 
1990: The Tower is closed to the public and the 17th commission to study the Tower's lean is convened. 
1995: During the installation of underground stabilizing cables the Tower nearly collapses. 
1999: Using a process known as soil extraction, engineers begin work on a long-term solution to promote the Tower's stability. 
2001: The Tower re-opens to the public.

See also:
Lean Into It: A new slant on the leaning Tower of Pisa