I would like to know if I should use "important for" or "important to" in the following sentence:

If you would be so kind as to accept this invitation we will arrange your stay in such a way that you will have a chance to visit and explore the surroundings and the history that was so important for Hanna.

Yours sincerely,

Both are OK. If you are speaking of the history, etc, that Hanna observed and admired, use 'to'; if you are speaking of the things that influenced her relatively unconsciously, use 'for'.
Thank you so much for your help!