This article includes a list of references, related reading, or external links, but its sources remain unclear because it lacks inline citations. Please help improve this article by introducing more precise citations. (September 2024) (Learn how and when to remove this message)

The Belchen system comprises five mountains with the name Belchen around the point where the borders of Germany, France, and Switzerland meet. The term is an extension of the Belchen triangle. The mountains are:

• Belchen, or Black Forest Belchen
• Belchenflue, or Swiss Belchen
• Ballon d'Alsace, or Alsatian Belchen
• Grand Ballon, or Great Belchen
• Petit Ballon, or Little Belchen

The heart of the Belchen system is the southernmost mountain of the Vosges, the Ballon d'Alsace (Elsässer Belchen or Alsatian Belchen, 1,247 metres). Seventy three kilometres due east is the Black Forest Belchen (Schwarzwälder Belchen, 1,414 metres), which is only 167 metres higher and over which the sun rises at the equinoxes, i.e. at the beginning of spring and autumn, as seen from Grand Ballon. Conversely, the sun sets over the Alsatian Belchen on these days when seen from the Black Forest Belchen.

Viewed from the Alsatian Belchen at the time of the summer solstice, the sun rises over Petit Ballon (Kleiner Belchen or Little Belchen, 1,272 metres), 27 kilometres away to the northeast. At the winter solstice it rises over the Belchenflue (Schweizer Belchen or Swiss Belchen, 1,099 metres), 88 kilometres to the southeast. Thus from the Alsatian Belchen the start of all four astronomical seasons is defined.

The region of the Belchen system is known today as the Upper Rhine, the Regio Basiliensis, the Dreiland or RegioTriRhena.

• Mountains of the Belchen system
• 
  Alsace Belchen
• 
  Little Belchen
• 
  Great Belchen
• 
  Black Forest Belchen
• 
  Swiss Belchen

• Belchen Tunnel under the Belchenflue

• Walter Eichin, Andreas Bohnert: Belchensystem, in Das Markgräfler Land, 1985, Issue 2, pp. 176ff.
  • Astronomisch-kalendarisches Ortungssystem, in Jurablätter, 5 May 1988
• Rolf d’Aujourd’hui: Das Belchensystem, Basler Zeitung, 18 June 1992

• Rolf d’Aujourd’hui: Belchen, Historic Lexicon of Switzerland, retrieved 20 May 2013
• Karl Rammstein: The Belchen Legend, 13. Juni 2004, retrieved 20 May 2013
• Hannes Hanggi: Ich will das System verankern (pdf; 844 kB), Basler Zeitung, 8 December 2007, retrieved 20 May 2013
• Gianni Mazzucchelli: Der Sonnenkalender von Rothenfluh - Das Belchen-System Archived 2016-03-04 at the Wayback Machine (pdf; 9.5 MB), retrieved 20 May 2013
• Belchen, guajara.com, retrieved 20 May 2013
• regbas.ch: Belchen Triangle explained, with illustration
• Reference at archaeobasel.ch: Projekt Archäo-Geometrie – Belchendreieck (PDF; 160 kB); im Jahresbericht der Archäologischen Bodenforschung des Kantons Basel-Stadt 1993, incl. bibliography
• Das magische Dreieck SRF broadcast from the series: Mysterious Switzerland