Learning new skill will make you smarter. Something completely different from what you usually up to. If you spend most of the time reading books try tennis or dancing lessons. This will give you a new perspective.

Traveling is very useful due to the all the same reasons. You learn a lot of new things and getting a new perspective.

Being physically fit plays a huge role in your mental abilities and it's proven by many researchers.

To sum it up, the more diverse is your experience and the more things you try the better.