Background
This is one of many musical works in 19th century that was based on Goethe's Faust. This popular poem was used by many composers to set to music, including Wagner, Schumann, and Liszt. Berlioz first read the French translation of the poem when he was a 23-year-old medical student and he was immediately fascinated by it. He made two attempts at setting the story of Faust to music. Shortly after he had read the story, he composed eight pieces of music depicting eight scenes in the poem. Soon displeased with them and having a grander plan for a larger work, Berlioz withdrew them from publication and destroyed any copy he could find. The second attempt, which is the current form of Damnation, was much grander in scale, and the movements flow from one to another more smoothly in telling the story of Faust.

The Tavern and the Opera
The Damnation of Faust was composed as a 'dramatic legend' rather than as an opera, and is usually performed in concert form rather than in a staged form with costumes and scenery and contrived movements as is the case with 'real' operas. It is considered an opera because it has been staged as such and also because if one closes one's eyes, most of it sounds like an opera, and quite a dramatic one at that. More important from our point of view, Berlioz gives us Auerbach's tavern while the more familiar Faust operas of Gounod and Boito do not. In this I am following the practice I began in the item about Chez Bancelin from Auber's Manon Lescaut in using a lesser known opera with a more substantial bar or restaurant setting.
Auerbach's Cellar in Leipzig is the first stop of the tour Mephistopheles puts on to show Faust what the good life is about after they have made their infernal bargain. There is much loutish behaviour, and Faust is eventually disgusted and leaves. After this, of course, there are much more attractive pleasures presented him, and he duly succumbs.
Berlioz follows Goethe quite closely in this scene. Goethe even gives a 'Song of the Rat' and a 'Song of the Flea' which Berlioz sets almost as is.

The Bar Review
Unfortunately, Goethe and Berlioz work hard at ensuring that we come away with a negative impression of Auerbach's Cellar. The place is really a representation for all that is low and wicked in the world. I suppose this is the result of letting intellectuals write plays on deep and ponderous subjects.
In the rear there are stairs leading up to the street. The atmosphere is close, dingy, smoky, and raucous. Around the dozen or so tables, the regulars are drinking and gambling. They are all regulars and they are all drunk. They all look like they have been drunk every day for the past several years. They are crude in language and behaviour, and often break into fights.
For all this, they do manage some pretty good bar room singing. Fortunately, the action takes place before the invention of the stereophonic electronic music destructor systems which have wreaked such havoc on taverns in our own time. There are four reasonably good drinking songs (which may figure eventually in the Drinking Songs category). There is a loud chorus to start, then Brander's Song of the Rat, followed by a delicious, if sacrilegious fugal Amen. Finally Mephistopheles gives us his Song of the Flea.