There are many urban paths in Oakland. According to a 2007 San Francisco Chronicle article, there are 230 usable stairways and paths in Oakland.
There is a book about them. There is a blog about them. Oakland Urban Paths leads monthly walks on them. There's even a PDF map of them and other paths. (Note this map is 10+ years old and hasn't been updated.)
The East Bay Express had a nice article, Staircases to Heaven, on February 26, 2014.