The photo was taken by Vadim Makhorov, one half of the rooftopping duo On the Roofs.
Cologne Cathedral is a Roman Catholic cathedral in Cologne, Germany. It is a renowned monument of Gothic architecture and is a World Heritage Site. It is also Germany’s most visited landmark, attracting an average of 20,000 people a day.
Construction of Cologne Cathedral commenced in 1248 and was halted in 1473, leaving it unfinished. Work restarted in the 19th century and was completed, to the original plan, in 1880. It is 144.5 metres (474 ft) long, 86.25 m (283.0 ft) wide and its towers are approximately 157 m (515 ft) tall. The cathedral is the largest Gothic church in Northern Europe and has the second-tallest spires after Ulm Minster. [source]