History of the Peloponnesian War

and he began immediately to assist in paving the way for their empire. It was by his advice that they built the walls of that thickness which is still seen round the Piraeus; for two waggons meeting each other brought up the stones. And in the inside there was neither rubble nor mortar, but large and square-cut stones wrought together, cramped on the outside with iron and lead. But only about half of the height he intended was finished.

For he wished by their great dimensions and thickness to keep off the attacks of their enemies; and thought that the protection of a few, and those the least efficient troops, would be sufficient, while the rest would go on board their ships.