We'd better have a look at some maps, so as to really understand where we are and where we're going.
First to the Piraeus, the harbour of Athens.

Look at the map in your book, page 102: the City of Athens. It shows the long, straight road between the Long Walls that Dikaiopolis and company had to walk along to get from Athens to the Piraeus. There they were going to try and board a ship that would take them across to Epidaure and to the healing powers of Asclepius, the god of medecine.

And on page 148 you'll see a photograph of the Piraeus, but viewed from a south-east angle, whereas the map on page 102 is viewed, like maps usually are, from due south.

A good place on the internet for these maps, with explanations about the different topics mentioned
     Map of Attica   for Athens to Epidaure
     Athens intra muros   for Athens itself
     Athens to Piraeus   for the journey made by Dikaiopolis and family