History of the Peloponnesian War

Now the wall of the Peloponnesians was constructed as follows. It consisted of two lines drawn round the place, one against the Plataeans, the other against any attack on the outside from Athens, about sixteen feet apart.

The intermediate space of sixteen feet was occupied by huts portioned out among the soldiers on guard, and built in one block, so as to give the appearance of a single thick wall with battlements on either side.