What were three contributions by Sumerians to the development of society and art?

From the time farmers first settled in Sumer around 5000 BC until the Amorites invaded the area around 2000 BC, many advances were made that brought this culture from a primitive farming society to a more organized civilization. Here are 3 areas in which the Sumerians left notable contributions:
Land in Mesopotamia was flat and conducive to farming, and by building ditches and canals to store water from the annual flood, the Sumerians were able to irrigate fields without waiting for rainfall. This allowed them to successfully grow enough crops for everyone, providing opportunity for some individuals to learn specialized skills such as pottery and weaving.
Sumerians were skilled in artistic areas such as metalworking, using copper, silver, and gold to craft objects like knives, helmets, and sculptures. They formed clay pots by hand until the potter's wheel was invented around 3500 BC. Wheels were soon utilized not only for pottery, but also for propelling carts and chariots, which revolutionized the load one could carry by donkey.
Small farming villages evolved over time into large walled city-states, each with its own temple and a ruler who controlled the surrounding farmland. Writing likely developed there as a method for keeping record of farmers paying their share of crops to the temple, and over time, writing progressed from simple pictograms to cuneiform writing which was composed of wedge-shaped symbols rather than crude pictures.