Travelers to Saint Petersburg beware-the metro is changing!
When I moved here in 2004, there were 4 lines. Small, but easy to navigate! Over the next few years, some new stations opened at the ends of those lines. Meanwhile, construction was going on to create some completely new lines.
As I entered the metro today, I learned that the line had changed from orange to purple and would branch off in a new direction. The map inside the metro car hadn't been updated yet, so it took me a few minutes to get my bearings.
The metro plan above is projected for 2030.
This is what it looks like now, as far as I know (click to enlarge):
I found this site to have some good information, although it is in Russian.