A long break after a long time

Am very happy and relaxed currently since I'll be on a
leave for four months tomorrow onwards. My office is
quite far away from my house hence I have always been
physically and mentally stressed by traveling that far!

Also, I am not a part of any big team in the office.
For past 3 years I have been working alone - talking to
myself and the walls!
Working alone always is NOT fun! Yes I know what I
am talking about.

I haven't though yet planned how to spend the holiday
time such that the mind gets relaxed as well as I do
something constructive! ;D

I can't plan outdoor trips.
What and how activities should be planned during this
break so that my mind is rejuvenated and at the same
time I don't feel that I am wasting time?

Any ideas?

Profession: Software developer
Hobby: Photography and writing softwares from scratch.