Two great ramparts that protected the roadway from Athens to the sea?

The ramparts didn't protect Athens from the sea, they provided a secure connection between its port and the walled city, so that even if the city was beseiged it could still ger in its food by sea, and still man its navy to harrass the home countries of attackers.

They were called the Long Walls, running parallel to each other from the port of Piraeus to the City