Caveman2Cosmos is a CivFanatics community mod that add new features and content to the Civilization 4 experience, with almost daily updates since November 2010. It is the spiritual successor the The Civilization 4 mod Rise of Mankind and its addon A New Dawn, and combined the work of over 100+ modders to create a mod to "rule them all". It is developed by StrategyOnly Productions with its modding team made up of prominent members of CivFanatics.
This mod is a very fun mod indeed! It has lots of content that can take about hours or even days (maybe weeks) to finish one game. This mod also have lots of replay value so in every game, you will never see the same things from a previous game.