http://www.idbsu.edu/courses/hy101/peloponn/03.htmThe Peloponnesian War - Page 3 of 17
He finally arranged peace with Persia, in 449, a peace that lasted almost 40 years. That treaty in turn allowed Pericles to transfer the treasury of the Delian League to Athens, where it became a convenient and deep extension to the city treasury.
The sudden influx of wealth
paid for the beautiful Parthenon and other statues and buildings. It paid
also for the fortification of the
Piraeus, making the port of Athens vulnerable only by sea. And from the
port to Athens itself he caused to be built the famous Long Walls--a pair
of walls seven miles long with space between them for four wagons across.
The Long Walls, and the fortifications at Piraeus, essentially extended
Athens down to the sea, where her magnificent navy ruled.