The
apsidal hall
has a mosaic floor with a decoration dedicated to the myth of
Arion
, who charms marine animals with the sound of his cithara.
All the decoration refers to the sea, populated with mythological creatures. The mosaic composition of a large
Oceanus
head oversees the scene, in a dominant position at the base of the apse. 
The room is quadrangular in shape and is located in the central part of the south main apartment, with a large opening onto the semicircular portico that gives access to the various spaces of the apartment.
The hall ending in an apse, covered by a semi-dome, was originally lit by three windows at the back and others in the side walls; 
scholars have hypothesised that this room was used by the Dominus as a
Diæta
or library, or even for
symposia
accompanied by music related to choral opera.
The hall of Arion is very much a room of importance. Together with the Diæta di Orfeo 
and the Sala della Piccola Caccia, they are the only rooms of the Villa embellished with two columns placed at the entrance, to underline their more dignified function.
