What event in 1170 may have caused the creation of 5,000 km2 large shallow bay of the North Sea in the northwest of the Netherlands?
Zuiderzee The Zuiderzee (] ; old spelling "Zuyderzee") was a shallow bay of the North Sea in the northwest of the Netherlands, extending about 100 km (60 miles) inland and at most 50 km (30 miles) wide, with an overall depth of about 4 to 5 metres (13–16 feet) and a coastline of about 300 km (200 miles). It covered 5,000 km2 . Its name means "southern sea" in Dutch, indicating that the name originates in Friesland, to the north of the Zuiderzee (cf. North Sea). In the 20th century the majority of the Zuiderzee was closed off from the North Sea by the construction of the Afsluitdijk, leaving the mouth of the inlet to become part of the Wadden Sea. The salt water inlet changed into a fresh water lake now called the IJsselmeer (IJssel Lake) after the river that drains into it, and by means of drainage and polders, an area of some 1500 km2 was reclaimed as land. This land eventually became the province of Flevoland, with a population of nearly 400,000 (2011).
Naval war on Lake Constance The naval war on Lake Constance (German: "Seekrieg auf dem Bodensee" ) was a series of conflicts that took place on Lake Constance, beginning in 1632, in the context of the Thirty Years' War (1618 to 1648). At that time various powers ruled different parts of the shoreline: in the north and east was Roman Catholic, Habsburg Anterior Austria; in the northwest and west the troops of the Protestant Duchy of Württemberg with their allies from Kingdom of Sweden and Kingdom of France. These various powers sought, for strategic reasons, to exercise their hegemony over the area of Lake Constance. Only the partly Catholic and partly Protestant southern shore which belonged to the Old Swiss Confederacy maintained an uneasy neutrality due to their divided loyalties.