Andron A. It was built by Idrieus (351-344) and had a front of 12 m. of width and 10,5 of height in marble, with two Ionic columns and a Doric frieze with triglyphs. A notice at the site indicates it must have had couches along the walls and probably in a niche in the back wall statues of Mausollos and his wife Ada as well as Zeus, the god.
An Andron was (I found this on the web) a feature specific to a Greek house, and it existed largely for the purpose of entertaining guests. This room was the only room in a Greek house reserved exclusively for the men of the household. It was found in the homes of the middle and upper classes, and thus was a mark of privilege. So was its main event, the symposium. The andron was not a place for women, or at least not respectable women, so when the house was large enough to allow it, this room was placed as far from the womens’ quarters as possible. The appearance of the interior made it clear it was intended as public space, for entertaining visitors from outside of the household. The luxury and extravagance of its decor generally distinguished the room from the rest of the house. The furnishings in the andron were usually the finest in the home. In fact, a majority of the most prized domestic objects recovered from antiquity were created for use within the andron.

In spite of all this I saw elsewhere that "men's room" more generally meant "dining room". This indicates that the building (in this particular spot, a religious settlement) was to serve for ritual dining after the sacrifice at the altar of the god.