The only way to really avoid younger people is to go to upscale establishments which are over their budgets. Drinking in Paris is already expensive enough, so I don't mind mingling with the younger crowd, which is generally not rowdy or loud.

Since nobody else is saying anything, I will direct you to the 11th arrondissement (of which Bastille is a part), but more precisely to the rue Oberkampf. It is very lively at night but considerable more sedate than rue de Lappe/rue de la Roquette near Bastille.

There are bars and restaurants to cater to all categories: loud places with rock music, quiet places with bookcases and everything in between.

I made a sort of photo report about it some time ago: http://www.fodors.com/community/europe/paris-the-bars-and-restaurants-of-oberkampf.cfm

Just to back up what kerouac said, I too was going to suggest the rue Oberkampf/rue Jean-Pierre Timbaud area.

I don't really know what you might be looking for (in terms of type of bars), but I would say the 11th is a good enough place and has a few hotels, or at least a few just on the other side of bd Beaumarchais, also.

I suppose St Germain would also be a good place for you. The main places I know that are underground are in the Latin Quarter, there are a couple of them like Caveau de la Huchette. That isn't exactly a "bar", though, but a place for live music and some dancing. I don't know of any places that are just bars that are in tunnels, but I don't get out much, anyway. Some of the other bars in the Latin Qtr mid area might be younger (and there are some younger places in St Germain, also).

Oberkamp, for sure (and I'm well past my 30s).

There is a place in the 11th that has old cellars but it is mostly for receptions and private functions. However, on the 1st and 3rd Thursday of the month it becomes a medieval tavern, if those dates coincide with your visit:

http://www.lescaves.org/

The underground parties you are referring to are invitation only. There are no legal clubs allowed in the Paris underground. And the only people I know who have partied there recently are very young.
I was also going to suggest Oberkampf.

Thank you all very much for your detailed and helpful replies! This is exactly the information I was looking for. I love Fodors. Thanks again!

To Christina-I think what you are referring to in the Latin Quarter might be the place I'm thinking of. Live music and dancing sounds perfect-I realize now that the term "bar" probably has a totally different connotation in Paris, whereas we in Ohio use it to mean any drinking establishment at all...
Many thanks!

The only problem is that there is not much other variety for that sort of place in the Latin Quarter. Oberkampf and Bastille multiply the options by 20.

I'd also assume that the Latin Quarter might be more likely to have a younger crowd as well with the Universities so close by.

Yes, I think oberkampf sounds like the place to stay as well as hang out, but a visit to the Latin Quarter sounds like a good idea.
Thanks all!

Also...Can anyone advise me as to how to delete a very old post that is no longer relevant, or is that impossible? Many thanks!

Once something is posted, it can't be deleted unless you write to the moderators and ask for it to be removed.

Okay, thank you!

While we're at it, does anyone have personal experience of this place in rue Galande in the 5th?

http://www.bonjourparis.com/story/caveau-des-oubliettes/

I stayed across the street upstairs (up many stairs) for 12 nights last year and didn't hear a thing (being half deaf helps). Gets good reviews - appears to be good value, with a good variety of gigs - and, although attracting a young crowd, a 51 year old on TA felt welcomed and not out of place at all.

I went to the Caveau des Oubliettes several years ago with my daughter. Had a great time, listening to music and talking to people we met there.

Good to know, thanks Nikki. Next trip will probably have a student daughter along so chances are we'll take the opportunity to check it out, especially if staying again at one of the very nice Paris Bestlodge properties opposite.