I collect postcards. Postcards from other countries.
I started that because I didn't have many chances to go traveling abroad. I really wanted to see what other places/cities are like, so I asked my grandma to bring some back as presents when she joined a tour. In fact, only those most amazing views get to be printed on postcards. It saves tourists time and money to develop bad pictures.
Then, some of my close friends did that for me as well. My collection got bigger and bigger slowly.