Law Code of Hammurabi
Carved into an 8 foot high chunk of Basalt, Hammurabi's law code is the first known codified (written) law. It is important because it represents a major advancement in methods of government. A written law implies that the law is equal for all men. The king can no longer change the law to suit his own whims; what is written applies to everyone.
The Stele of Hammurabi (see picture below), found in 1902, lists all of the laws in neat rows of Cuneiform.