They started in 1990 by slowly adding lead counterweights to one side of the tower on the north (the direction it was leaning). This had a significant impact, reducing the lean by 17 inches (43 cm) and stabilizing it.

Extracting soil from underneath:

In 1999, engineers decided to try excavating soil from the opposite side of the tower, beneath the raised side, to allow it to settle back down. Over three months, they moved around 38 cubic meters (1,342 cubic feet) of soil. As a result, the tower straightened a bit further, by about 1.4 inches (3.6 cm).

Installing tie-down cables:

In order to keep the tower leaning slightly inward now that it had been straightened, they installed tie-down cables which act as guy wires, extending from the top of the tower and anchoring deep into the ground.

Closing to tourists:

During most of the stabilization work, the tower remained accessible to tourists. However, as a safety precaution, it was completely closed for 11 years from 1990 to 2001.

Continuous monitoring and adjustments:

Even though the tower has now been straightened and seems stable, engineers continue to closely monitor its movements using tilt sensors and other technology. Regular maintenance and adjustments are made as needed to ensure its safety and stability in the long term.