This is one of my treasured possessions, a flattened penny that I made at the World Trade Center on a visit there in the late 90s. I made it in a machine on the top floor (on the viewing deck).
I remember being a little scared at how high up we were. I think people who have never visited might have a hard time visualizing just how incredibly high that building was.
I also bought this postcard in the WTC gift shop when we were there.