Cologne Cathedral Crane

Early medieval cranes could usually move loads only vertically, requiring additional equipment for horizontal transport. The Cologne crane, by contrast, could swing its load along a circular path and – thanks to a rope run of about twenty metres from the jib tip to the drop-off point – draw the load several metres out of the vertical. Its working area was a ring, reaching almost every part of the tower's masonry. This eliminated transport across the site and allowed lighter scaffolding, since it now had to carry only workers, not heavy blocks.

The 25.10-metre-high supporting frame, made of oak beams roughly 30 by 30 centimetres thick, was clad in slate and formed a 12.80-metre truncated pyramid on a square base; its side length tapered from 9.73 metres at the base to 4.70 metres at the top. At its centre stood an upright, 15.20-metre round oak beam known as the "Kaiserstiel" (imperial mast). It rested on a pear-shaped wrought-iron pintle in an iron bearing socket, which let it rotate easily. This rotation also protected the crane in storms, since the jib could turn with the wind. The 13.15-metre jib projected 10.55 metres horizontally from the "Kaiserstiel"; when work stopped, its tip lay about 70 metres above the ground. The crane rested with the corners of its frame on four wall sections of the tower, keeping the corner piers accessible. Arnold Wolff suspects the crane was built at foundation level and climbed upward with the tower, being raised corner by corner with wedges – roughly every six months across the whole construction period.

For more than 500 years the crane was a defining feature of Cologne's skyline and, for its people, a symbol that cathedral construction had not been abandoned but merely paused. Residents read the wind direction from it; when it turned in the wind at night, a characteristic sound carried across the whole city. When the jib had to be removed on Prussian orders in 1816, it provoked vigorous protests from the citizens. Its unmistakable silhouette served as the emblem of Cologne, much as the cathedral's twin towers do today, and appears in numerous chronicles and cityscapes of the 15th and 16th centuries, such as the Nuremberg Chronicle (1493) and the Koelhoff Chronicle (1499). The document sealed into the final stone at the cathedral's completion in 1880 still referred to the "Domkrahnen, the old landmark of Cologne."