Rome was the capital of the world at the time this was written.  It was the influential center of culture and philosophy and it was to a group of faith-strong Christians in this area which Paul addressed.  There are many points of focus in this letter but God's process and plan of justification for the sinner stands out prominently.  What we are without Christ and left to ourselves is primary in the first few chapters.  Then, the true state of the believer before God is clearly presented to show the "power" from which we live, and the fundamental "doctrines" which clarify true truth.  This letter is foundational to so much of "the Faith" that it is worthy of consistent, detailed study.