Cologne Cathedral.

“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. The cathedral is the largest Gothic church in Northern Europe and has the second-tallest spires. The towers for its two huge spires give the cathedral the largest façade of any church in the world. The choir has the largest height to width ratio, 3.6:1, of any medieval church.”