Collect stamps

A lot of attractions, places, temples, subway stations,... have their stamp it's a super fun souvenir to collect them in a little book.

There are also the Goshuin (large stamps, handwritten by monks, that work as a kind of proof that you have visited a specific temple or shrine) which can be collected , these ones you have to pay for & usually stay in line. In the Golden Temple you get one as a souvenir as your ticket.

We have read that it's it is considered proper etiquette to collect stamps from Buddhist temples in one book and stamps from Shinto shrines in another separate one.