A building site that stayed open for 632 years.
On 15 August 1248 Archbishop Konrad von Hochstaden laid the foundation stone of Cologne Cathedral. Work stopped around 1560, and for centuries a crane sat on the half-finished south tower. Building resumed only in 1842, and on 15 October 1880 the cathedral was declared complete – 632 years after the first stone.
Useful: Great buildings are rarely one generation's project; they are relay races across centuries.
Source: en.wikipedia.org