From here, the speaker faced northeast, and addressed the audience. This was the arrangement in the latter phase of the Pnyx's life. Previously, (from c. 6th century BC) the bema (speaker's podium) was in the north and the audience faced the Agora.
Spoke here: Themistokles, Perikles, Demostthenese and Aischines.
To the speaker's left and right, the rock ledge from which the bema was cut has been cut away to make a "wall", at least 8 feet high in many places. (The cutting away made a vertical face in place of the natural slope.)
The underlying hill falls away to the north of the bema, but a semi-circular retaining wall was built, and the area inside it filled in, to provide fairly level ground in front of (northeast of) the bema.
(Information from Greek ministry of culture sign at site.)
Category: ancient