How expensive is Rome? And what are fun things to do/see?

Rome is not as expensive as other European cities such as London or Paris, but it is not cheap either. The thing I enjoy about Rome is that the city itself really isn't that large; everything is in walking distance. The subway is cheap and incredibly easy to manage. There is line A and line B. They cross at Termini Station which is the "Grand Central Station" of Rome. There is so much to see and do. You'll wish you had a week for the Vatican Museums alone. I'm not sure about the clubs. I really didn't like going out after dark. Also, be prepared to see graffiti everything. I was very surprised by this.