Modern art defines for buildings

[Caesium]

I heard somewhere, that also buildings can have modern art define.
I'd like to add modern art define tags to existing art defines, to have the same effect as with units, when they change their look to modern.
And here's my question: How do I do this?

 

[Osymandias]

it's easy!
it is defined in the CIV4CityLSystem.xml, and there you should search teh entry for the lighthouse. it's the way i did it and added a new ancient and classical model and skin.