The Black Forest is a hundred and sixty kilometres long, and anyone treating it as one place spends the day in a car. In practice it divides into three: the north around the Schwarzwaldhochstraße with the Mummelsee and the Hornisgrinde, the middle around Triberg with the waterfalls, and the south around the Titisee, the Schluchsee and the Feldberg. Two and a half hours of driving separate the northern end from the southern one. A session stays in one of the three.
The real subject is a temperature inversion. From late September into November the air cools overnight in the valleys, the fog settles in the bottom of them, and at eight hundred to a thousand metres you stand in clear sun above a closed sea of cloud. It can be read off the forecast the evening before, which makes it plannable — unlike almost everything else in this catalogue. The price is the hour: by nine the fog has often burned off, so a session like that starts before sunrise.