Of course, you can always make your entrance on foot, walk past pristine chemists and quaint patisseries, past the Roman baths and town church to one of the many cosy hotels that German pensioners love to visit. It is a deeply conservative, conventionally religious environment that harbours at least one unexpected secret: a prestigious avant-garde musical life. Pierre Boulez has been to Badenweiler; so have Luciano Berio and Gyorgy Kurtg.
Every year the Hotel Romerbad hosts a run of important concerts, but the star act springs to life in early summer when Manfred Eicher, the team from his ECM record label and a whole roster of his artists launch a three-day festival of mostly contemporary music.
Year after year the same people return, but Eicher's community of listeners continues to grow. "The intensity of their listening is incredible," he tells me, and he is not exaggerating. I watched their faces - many of them old enough to have witnessed a pre-war avant-garde - as Jon Christensen teased his drum-kit to life like a slow tide draining across pebbles. That was on Friday at 5.30pm (such a sensible time for a concert), when pianist Ketil Bjornstad structured chords with the kind of space-sensitive intuition that informs most of Eicher's recorded productions. Bjornstad provided a warm bed of harmony, while cellist David Darling bowed a mellow melody line and electric-guitarist Terje Rypdal set to work with a disorientating blend of musical poetry and improvised chaos.
Nothing that we heard could have been safely categorised either as "jazz" or "concert music", and yet the audience hung on to every note, happy to go wherever Bjornstad and his men took them.
Bjornstad paid tribute to Eicher by naming him the "fifth" member of the quartet. What exactly did he mean? "The role of the producer is, first and foremost, to be a listener," as Eicher put it to me after the concert. "The way I listen is the way I record. Listening should never be neutral; it should be personal. This `first' listener should also be someone with a sense of perspective, someone who gets involved with a piece, talks about its architecture, its dynamic spectrum and the frame in which the music is going to happen. If musicians welcome me in this sense, then it's the kind of respect that touches me deeply," he says.
An active response to sound is also crucial. "As Glenn Gould said, the role of a producer is as much to do with `sounds' as with artistic partnership. Every artist needs - in the solitude of his own decision-making - a reflector, and I see myself as someone who responds in a musical context. I do not see myself as being involved in any aspect of so-called marketing of the music, which is something that comes afterwards."
Still, he was visibly delighted when his British distributor (New Note) awarded him a golden disc for 100,000 British sales of Jan Garbarek's Officium album.
He dislikes what he calls the "cliche" of an ECM "sound", and would rather talk in terms of the label's individual approach to programming. Eicher was a self-effacing presence at the concerts, smiling quizzically from an end seat and signalling his thanks to the players as they walked off for an interval drink.
Saturday's programme was a celebration of violists in duet, with George Benjamin's busy Viola-Viola as its prompting idea. The girlish but intense Kim Kashkashian partnered Garth Know, formerly the Arditti Quartet's violist, in a programme that shared the rigours of Scelsi, Kurtg, Berio and Radulescu among two, with Isang Yun's long-drawn Contemplation testing the audience's powers of concentration, and Bartk (a sequence of earthy duos) the winning card.
The trumpeter Markus Stockhausen (son of Karlheinz) called the tune for the third and last concert, with Arild Andersen, a spectacular bass player, keeping things candidly conversational. David Darling marked his unscheduled return for a testing - and teasing - bass/cello duet. At one point Jon Christensen made music by tapping on his drinking glass before swallowing its contents.
That guy can magic more expression from a drum-kit - with or without sticks, on skin or on metal - than most string players can manage with a bow. He'd sit there, aiming his brush before deciding when or where to strike. And when he did, his timing was always spot-on.
Eicher's artists are usually outreaching and unpredictable, but Sunday's final act - indeed, the last act of the festival - was, in some respects, the most surprising of all. Gianni Coscia donned his accordion while Gianluigi Trovesi employed three varieties of clarinet for a programme that ranged from Kletzmer-style dance-music to John Lewis's Django and a whole string of bittersweet morceaux. For the first piece, Coscia sat alone on stage while Trovesi soulfully played his way downstairs from the first tier, and a similar end sequence brought us full circle. It was street-band stuff, mostly jolly, but tinged with disquieting sadness. I doubt that the region has heard anything like it in years.
While most stamped and cheered, one listener grumbled "Not ECM's usual style". Actually, it was typical. Many pieces ended on a musical question, which is where the grandeur of Badenweiler comes in, with its endless potential for reflection and solitary wandering.
"The influence of the surroundings, and of nature in particular, is there - whether you're aware of it or not," says Eicher. "And although I don't believe that music `belongs' in any fixed location, having an audience in such close proximity - and enjoying such a dedicated following - allows us to create a very special way of experiencing music."
And if you don't fancy travelling to Badenweiler, the first British ECM Festival will kick into gear in Brighton this November.