There are ambitious Minecraft mods, then there's the kind that tries to turn Mojang's game into one of the best (and most epic) strategy games of all time, Civilization.
CivilizationCraft, as it is so un-catchily named, does just that. You play like any other Civilization game, building your nation from one settlement to a globe-spanning empire (or 'civilisation', if you will).
The multiplayer mod features a lot of what makes the Civ series so great, like trade goods, conflicts, tech trees, spies, wonders and diplomacy, among many others - oh, and mining. Because it's Minecraft. Obviously.
You can see more images and read more in-depth descriptions of what CivilizationCraft entails right here. Try and resist getting involved after drinking all that in, I dare you.