The vistas from the Jura High Altitude Trail to the south are often spectacular, with the Swiss Plateau hiding under a thick layer of fog.
The Swiss Plateau [in German: Mittelland] is approximately 50 km wide; it is partly flat but mostly hilly with an average height of about 580 m. Thirty percent of Switzerland’s surface are covered by the plateau. It is by far our most densely populated region, and the most important with respect to economy and transportation.
In the winter half-year, the air on the Swiss Plateau can stay still, building a lake of cold air and often a ceiling of high fog. These clouds look like an ocean of fog when seen from above [usually above 800 m]. Hence, it is called the ‘Nebelmeer’ [Nebel = fog; Meer = sea]. Sometimes, this sulky, ‘inversion’ weather lasts for days or even for weeks, during which the neighboring regions of the Alps and the Jura may have bright sunshine.