FrancophonIA/Vikidia-EnFr huggingface dataset:
Lake Constace or Lake of Constance (German: Bodensee) is a large Lake on the river Rhine. It is on the border between Germany and Switzerland and Austria. It is the third largest lake in Central Europe after Lake Balaton and Lake Geneva. It is made of two smaller lakes (called Obersee and Untersee (Upper and lower lake) respectively). These are joined by a small part of river in Constance.
The lake covers about 564 km2 (218 sq mi) of total area.

There are three big islands in the lake. The islands Lindau and Mainau are in the Obersee. Reichenau is in the Untersee. The Obersee is about 63 km (39 mi) long, from Bregenz to Bodman-Ludwigshafen. It is about 14 km (9 mi) wide at its widest point between Romanshorn and Friedrichshafen. The deepest point is 254 m (833 ft) deep, between Fischbach and Uttwil (just off Constance).

The lake forms the border between Austria, Germany and Switzerland. On much of its length, this border has not been defined. Switzerland thinks the border runs through the middle of the lake. Austria thinks the lake is a condominium of all the countries. A condominium is a space that is governed by all countries taking part in it. Germany has no clear view.

Other legal issues, like navigation and fishing are governed by separate treaties. About 62% of the lake's shoreline belongs to Germany, about 33% to Switzerland, and the remaining 11% to Austria.

In 1963, the whole lake froze. This has not happened since then.