Final answer:
There were originally 12 poleis in Attica, and Athens grew so powerful that it absorbed the other 11.
Step-by-step explanation:
The original number of poleis found in Attica was 12.
Out of these poleis, Athens grew so powerful that it absorbed the other 11 poleis. Athens became a major force in Mediterranean trade, had a rich and populous population, and was at the forefront of political innovation. This led to conflicts over wealth distribution and political power, but Athens managed to establish its own empire.