Long lasting structures: a comparison
The top three things that decide a building's longevity are: 


The roof
The roof 
The roof


So, if you are serious about this, there are two ways to go.  

Invent a 1000 year roof

Good luck.   Nobody has figured out that one.   Well, cavers have. 

Make a structure that will last 900 years after the roof fails.

This is the fun one!  Heck, it's be worthy of a doctorate thesis.  

When the roof fails, make the rest of the structure stable enough that the next guy can just put another roof on it.  

Fortunately you're in Europe, where there are thousands of ruins to study, so you have lots of examples of what has worked in the past.   You can blend this with the latest fabrication tech. 

By the way, concrete does not have a 100 year life.  There is 2000 year old concrete out there.  The biggest problem in concrete is the use of steel reinforcing rod, which oxidizes when exposed to water and expands when it oxidizes.  This causes a "jacking effect" which greatly worsens water leakage and ultimately shatters the concrete structure.  There are other re-rod materials which do not do that, they are not used because they are more expensive.