Rhye's and Fall of Civilization ("RFC"), previously named "Rhye's Catapult project", is the sequel of Rhye's of Civilization.
Rhye's and Fall of Civilization is a modpack for Civilization IV that attempts to make your single player game an "Earth simulator".
It can be considered both a mod and a dynamic scenario: Rhye's and Fall of Civilization revolves around the re-enacting history on Earth, guiding your game in through an alternative, but still realistic history, unique every game you play.
This mod doesn't feature loads of new units, civilization and other "stuff": it's focused on new concepts.
Due to the very high quality and popularity, this mod shipped with the 2nd Civ4 expansion, "Beyond the Sword", in a enhanced version.
Then, what does it do to be so special?
The most important concept behind the mod is that civilziations don't start all at the beginning of the game, but appear at different times. For instance, picking the Arabs, the game will autoplay until 620 AD, when the player will take control and find a world that may have developed in an unpredictable way.

That said, it also features:

A 124x68 world map with enlarged Europe for better gameplay
Dynamic rise and fall of civilizations
Stability management: unstable empires will risk secessions and civil wars
Players can control more than one civilization in a single game (can take control of an ancient civilization and later "jump" to a new one)
Dynamic spread of resources
Civ-specific customised AI that adapts its behaviour to the Earth map and sends settlers to found cities in their historical place, with their historical name
Python events that reproduce historical attacks of the barbarians
Plague that will offer a hard challenge spreading throughout the world
Unique powers and victory conditions for each civilization (this feature has inspired Civilization Revolution)
Unique victory conditions for each civilization
World Congresses where cities are traded
World wars, thanks to a revised alliance system
New flag and new terrain graphics, including a new terrain: marshes
Rule changes that will give this mod the feel of old Rhye’s of Civilization
A new civilization: Babylon, and other non playable civs (for Warlords version only)