Of Andron B not much remains. It was built by Mausollos (377-352 BC), it had a 10,5 metres high and 12 metres wide marble front. It had two ionic columns and a Doric frieze. Inside there were couches along the walls for the sacred meal. In the niche in the back wall there were possibly statues of Mausollos, his wife Artemisia and the god Zeus.
The Dutch Wikipedia describes how an andron was a reception room for male guests. On an elevated platform a number of (often three) couches stood, the elevetation was to prevent the furniture from rot due to dampness. The dampness might develop because it was a habit to throw a bucket of water over the guests' heads in the morning, since they would get thoroughly drunk in the "symposion". In order for the outside world to know how jolly things were inside, the andron had, exceptionally, windows to that outside world, so the cries of joys could be heard.
Inside the room.