The other day I was looking for a game and Freeciv caught my eye.
The source package is very simple to install. There is an INSTALL document in the package that gives good directions. You can compile and play the game right in the same directory, or you can install it to a directory of your choice, like /usr/games.
The only stumbling point I ran into was I didn’t have sound support at first. I installed libsdl-mixer1.2-dev and re-compiled and all was well.
There are a few gameplay modes: basic single-player, scenario, and networked multi-player. Once you kick off the single player game, you can also take a look at some of the options to tweak the game as you like: