As with most European Medieval churches they built cathedral over the period of 2 centuries. Unknown to most of us now, the time lapse was not due to the construction, but mainly because of the costs.
In those days building a church meant using huge sums of money. They started building until the money was up. Then, a few decades in the future, they started again.
This cathedral was never completed. A large part of the church is still in the condition it was when they stopped building.