On October 15, 1880, Cologne Cathedral, Germany was completed 633 years after it was begun. From the article:
"History of Cologne Cathedral | Cologne Tourism
Christians began to celebrate religious services at the location of today’s Cologne Cathedral in Roman times. After Archbishop Rainald von Dassel brought the relics of the Three Wise Men to Cologne in 1164, the Cathedral became one of the most important pilgrimage sites in Europe and required a new architecture.
The building plan for the Gothic Cathedral was drawn up by master mason Gerhard of Reil, who modelled the new church on the cathedrals of Paris, Strasbourg and Amiens. The cornerstone of the Gothic Cathedral was laid by Archbishop Konrad von Hochstaden on the Feast of the Assumption of Mary on August 15, 1248.
However, construction ceased in the 16th century, due to a lack of funds and a general disinterest in Gothic architecture. Building work was suspended for almost 300 years.
In the 19th century, people were once again interested in history, the Middle Ages, and the Gothic style. At the initiative of the King of Prussia, Frederick William IV, Cologne citizens founded the Zentral-Dombau-Verein (Central Cathedral Building Society), whose main task was to collect donations for the completion of the Cathedral. Prussia also helped to fund the construction work. One year later, the king laid the cornerstone for the continued construction of the Cathedral. Cologne Cathedral was finally finished in 1880, 632 years after construction originally commenced. The completion of the church was celebrated on October 15.
Although Cologne Cathedral was hit by several heavy bombs in World War II, it miraculously remained standing. However, it took many years to fully restore the building. In addition to the wounds from World War II, the damage caused by the weather and by pollution has to be repaired. As a result, Cologne Cathedral is a “permanent construction site”."