York Minster in England is mostly 1000 years old. There are some nice stories about how it handled a serious fire in 1984 here, (starting about 18 minutes in) https://www.bbc.co.uk/sounds/play/m0007pws. eg, the 2000 year old Roman drainage system got used for the first time in 1000 years because lots of water got inside the building from the fire hoses.

When rebuilding it, they had to decide whether to remake it in the same way it was originally, or to use a modern approach. They decided to use oak beams again because of lack of evidence about what happens to steel structures after hundreds of years. But then they couldn't find any oak trees big enough.