The popular tourist region of Lake Constance spans three countries. It is the third biggest lake in Central Europe and is on the path of the Rhine River. The lake shore is shared between the German federal-states Baden-Württemberg and Bavaria, the Austrian federal-state Vorarlberg and Eastern Switzerland.

All three nations have developed a specific culture around their part of the shore. Lake Constance is also notable for the boundaries not being agreed upon by the three countries having a shoreline on it. 

In practice this has few effects for the traveler because none of the countries in question grants ius soli citizenship and questions of migration are mostly irrelevant due to the Schengen Agreement. 

The lake is also a major source of drinking water for the surrounding regions.

- Wikivoyage