Themistokles started the construction of the wall guarding the road connectiong Athens and Pireas. He also encircled Pireas with circuit wall to protect the ports. These fortifications, together with the wall constructed by Kallikrates under the instruction of Perikles, ensured the supply from the sea during the time of war and the command of the Athenian navy. These wall, however, were later demolished, and were rebuilt during the period of Konon. The work started before he won the battle of Knidos, and finished some time after 346 BCE. We can see the ruins of these fortifications almost all around Pireas.
The first and the second photos were shot near the Marina Zeas.
This is the wall along the Odos Themistokleos.
This I found at around the western end of Pireas; it looks like foundation of a tower.