Archbishop Konrad von Hochstaden laid the foundation stone of the Kölner Dom on 15 August 1248. A new foundation stone for the continued building was laid on 4 September 1842. The official completion was celebrated on 15 October 1880. Since then the Dombauhütte, the cathedral workshop, has had the task of maintaining the building. Today it has about 85 employees from different trades. In 2020 UNESCO added the cathedral workshop tradition, nominated jointly by 18 workshops in five European countries, to its Register of Good Safeguarding Practices.