 Between 1989 and 2000 extensive engineering works were conducted to arrest and rectify damage and distortions caused to the structure by the uneven rate and extent of the sinking of the building provoked by the continuous settlement of the ground on which it stands.This began with the drainage of the lake of the Valley of Mexico initiated in 1607 and has continued with the reduction of the water-table caused by the pumping of water for use by Mexico City's rapidly expanding population.The last of the temporary props which had disfigured the interior of the building during the engineering works were removed on 28 November 2000.