I like the Geographic map mode. Granted it's not particularly useful when you're expanding your holdings, or fighting a war, etc.... But I find it pretty to look at, and relaxing along with some of the more relaxing peace-time music.
It is useful when fighting a war, it's the only time I use it - to get a quick overview of the terrain so I can pick my battlefield to ensure I'm defending in hills or mountains or attacking on plains.