Travel by train.

Okay, not that kind of subway. I was thinking more along the lines of massive exploration via local train/bus. I live in San Francisco, a city which includes TONS of various means of public transportation. For example, there are at least 20 bus routes on which I have never ridden. There are also numerous neighborhoods I have yet to explore. I recently found myself with not a single thing I HAD to do, so I hopped on a MUNI train at a given point on it's route and rode it until it ended. I hopped off, grabbed some hot chocolate (it was freezing!), took a few photos and hopped back on. While I was in parts of town with which I was familiar, I read my book. When it was unfamiliar, I just looked out the window and I stayed on until it ended on the other side of town. It was quiet, I got through a book I was reading, I saw much of this amazingly, insanely, over the top beautiful city, I took some notes about restaurants I have been meaning to visit and it only took a buck fifty out of my pocket. Solid day time activity.