Oops...missed Nostradamus quest

[Omnion]

I gave the spirit gem to DaVinci before getting the N. quest... He flew back to Barcelona, and now will not ask me about my progress. I seem to be stuck. What can I do to get the N. quest NOW? I've already cleared out the crypt and don't want to have to go back that far... The weird woman is no help yet...

[Crenshinibon]

Well, you can just keep playing.

Nostradamus's quest is optional. The only thing that happens, as far as i know, is you gain more experience (within the caves) and the ending movie changes.

[Ravager]

No, it's not optional, you have to complete both the Caverns and the Crypt. There should be another way of finding out where the Caverns are though. Try the titans in Toulouse if you haven't killed/driven them off yet.